Abhandlungen der k. k. geologischen Reichsanstalt 39-0143-0175

©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at Abh Geol B.-A ISSN 0378-0864 ISBN 3-900312-54-0 Band 39 S.143-175 Wien, März 1987 Upper Cretaceous Calcareous Nannofossil Biostratigraphy of the Southern Norwegian and Danish North Sea Area By CHRIS P MORTIMER*) With Figures North Sea Calcareous Nannofossils Late Cretaceous Biostratigraphy Contents Zusammenfassung Abstract Introduction Geological Setting Lithostratigraphy Method of Investigations Calcareous Nannofossil Biostratigraphy 5.1 Previous Studies in Upper Cretaceous Calcareous Nannofossil Zonation 5.2 Historic Reviews Constraints of the Study 6.1 Ditch Cuttings 6.2 Type of Drilling 6.3 Diagnostic Species 6.4 Preservation 6.5 Geological Structure Biozonation 7.1 Tertiary 7.1.1 Ekofisk Formation 7.1.1.1 Markalius inversus Zone 7.2 Late Cretaceous 7.2.1 Tor Formation 7.2.1 Arkhangelskiella cymbiformis Partial Range Zone NK1 7.2.1 Nephrolithus frequens Taxon-Range Zone NK2 7.2.1 Zygodiscus spiralis Interval Range Zone NK3 7.2.1 Gartnerago obliquum Partial Range Zone NK4 7.2.1 Phanulithus obscurus Partial Range Zone NK5 7.2.1 Reinhardtites levis Partial Range Zone NK6 7.2.1 Tranolithus orionatus Partial Range Zone NK7 7.2.1 Broinsonia parca Partial Range Zone NK8 7.2.1 Orastrum campanensis Partial Range zone NK9 7.2.1.10 Helicolithus trabeculatus Partial Range Zone NK10 7.2.2 Hod Formation (Early Campanian to Early Turonian Age) 7.2.2.1 Cylindralithus asymmetricus Partial Range Zone NK11 7.2.2.2 Broinsonia enormis Partial Range Zone NK12 7.2.2.2.1 Cribrosphaera ehrenbergii Interval Range Subzone NK12A 7.2.2.2.2 Lucianorhabdus cayeuxii Partial Range Subzone NK 12B 7.2.2.3 Watznaueria barnesae Assemblage Zone NK13 7.2.2.3.1 Ahmuellerella octoradiata Interval Range Subzone NK13A 7.2.2.3.2 Lithastrinus moratus Interval Range Subzone NK13B 7.2.2.3.3 Micula staurophora Partial Range Subzone NK13C 7.2.2.3.4 Prediscosphaera cretacea Interval Range Subzone NK13D 7.2.2.4 Helicolithus valhallensis Assemblage Zone NK14 7.2.2.4.1 Marthasterites furcatus Concurrent Range Subzone NK14A 7.2.2.4.2 Kamptnerius magnificus Partial Range Subzone NK14B 7.2.2.4.3 Eiffellithus eximius Partial Range Subzone NK14C 7.2.2.4.4 Quadrum gartneri Partial Range Subzone NK14D 7.2.2.5 Lithastrinus ssp Assemblage Zone NK15 7.2.3 Plenus Marl Formation (Late Cenomanian Age) 7.2.3.1 Barren/Impoverished Zone • 144 144 144 144 144 147 147 147 147 152 152 152 152 152 152 153 • 153 153 153 156 156 156 157 157 157 157 158 158 158 159 159 160 160 160 160 161 162 162 163 163 163 163 164 164 165 165 165 166 167 *) Author's address: CHRIS P MORTIMER, Robertson Research International, Ty'n-y-Coed, Llanrhos, Llandudno, Gwynned LL30 1SA, North Wales, United Kingdom 143 ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at 7.2.4 Hidra Formation (Cenomanian Age) 7.2.4.1 Axopodorhabdus albianus Partial Range Zone NK16 7.2.4.2 Parhabdolithus asper Partial Range Zone NK17 7.2.4.3 Cribrosphaera primitiva Partial Range Zone NK18 7.2.4.4 Gartnerago nanum Partial Range Zone NK19 7.2.5 Upper Cretaceous/Lower Cretaceous Boundary; Cenomanian/Albian and Hidra Formation/Robdy Formation Boundaries Conclusions Acknowledgements Appendix 1: Taxonomy References Zusammenfassung In dieser Arbeit wird ein Zonen-Subzonen Schema für kalkige Nannofossilien des Maastricht bis Cenoman (OberKreide) vorgeschlagen Die 19 Zonen und 10 Subzonen, die im südlichen norwegischen und im dänischen Nordseegebiet angewandt werden können, wurden anhand von detaillierten Untersuchungen an Kernen, Seitenkernen und Schlämmproben erarbeitet Diese Zonierung wird als praktisches Schema zum Gebrauch durch die Erdöl-Industrie vorgeschlagen Detaillierte Vergleiche mit den Arbeiten von SISSINGH (1977, 1978), PERCH-NIELSEN (1979a) und CRUX (1982) werden diskutiert Abstract In this paper a calcareous nannofossil zonal / subzonal scheme spanning the Maastrichtian to Cenomanian (Upper Cretaceous) is proposed The nineteen zones and ten subzones recognised for the Southern Norwegian and Danish North Sea Area have been derived from the extensive examination of core, sidewall core and, in particular, ditch cutting material This zonation is proposed as a workable scheme for the oil industry A detailed comparison with the works of SISSINGH (1977, 1978), PERCH-NIELSEN (1979a) and CRUX (1982) has been undertaken (as these are the most comparable schemes to the present study) Introduction Since the discovery of hydrocarbon bearing Upper Cretaceous strata in Amoco's 2/11-1 well (drilled on the southern flank of the Valhall field in 1969) much interest has been focussed on the Southern Norwegian and Danish North Sea Sectors Shortly afterwards Phillips giant Ekofisk Chalk Field was discovered and to date at least 16 commercial hydrocarbon fields have been discovered in chalks of Late Cretaceous and Early Palaeocene age (Fig 1) The lack of age diagnostic planktonic foraminiferal taxa and their general poor preservation has hampered the solving of stratigraphic problems encountered in developing these North Sea Chalk Reservoirs The potential biostratigraphic usefulness of calcareous nannofossils in the oil industry has only been recognised in relatively recent years following the publication of the comprehensive Tertiary zonation scheme of MARTINI (1971) which is now widely accepted The Upper Cretaceous, however, is not so well subdivided and it became clear that a new biostratigraphic calcareous nannofossil scheme was needed to improve chronostratigraphic control for hydrocarbon exploration The main objective of this paper is to introduce a workable Upper Cretaceous (Maastrichtian to Cenomanian) zonation scheme for the oil industry using calcareous nannofossils for the study area incorporating published nannofloral events where possible NB: For the purpose of this paper chronostratigraphic terms uppermost, upper, middle, lower and lowermost 144 167 167 167 170 170 170 171 171 171 173 refer to rocks whereas the geochronologic terms latest, late, mid, early and earliest are used for stratigraphic units Geological Setting The study area is located within the Southern Norwegian and Danish North Sea Sectors essentially centering around a Northwest-Southeast trending graben structure, (Fig 1), The geological development of the graben was probably initiated before the Permian (OFSTAD, 1983) A more detailed account on the geological setting as well as tectonic history of the area, ist given by ZIEGLER (1978) It is, however, important to note that the thick Upper Permian evaporites deposited in the Central Graben area have greatly influenced the geological and structural evolution of the study area (OFSTAD, 1983) Salt movements, which were initiated in the Late Triassic, continued in the Cretaceous and Early Tertiary and were responsible both for the formation of most of the hydrocarbon traps and also the significant fracturing recorded in the area The fracturing was very important as it provided conduits for hydrocarbon migration from the Upper Jurassic Kimmeridge Clay Formation source rock through the Lower Cretaceous sediments and into the Upper Cretaceous and Lower Palaeocene chalk reservoir rocks above Lithostratigraphy The lithostratigraphic terminology used in this paper follows the schemes of DEEGAN & SCULL (1977) and HESJEDAL & HAMAR (1983) A generalised stratigraphy for the Upper Palaeocene to Middle Albian interval for the study area is shown in Fig This study concentrates on the Chalk Group and in particular the Maastrichtian to Cenomanian interval The Chalk Group is overlain by claystones of the Maureen Formation (Early Palaeocene age) and these are in turn succeeded by a shale sequence representing the Lista Formation and a shale/claystone and tuffaceous claystone sequence representing the Sele and Balder Formations respectively (which are all of Late Palaeocene age) The Chalk Group comprises the Hidra, Plenus Marl, Hod, Tor and Ekofisk Formations The Ekofisk Formation, which is of Early Palaeocene age, consists of limestones which become increasingly more argillaceous towards their base The Ekofisk/Tor Formation boundary can be represented by a dark grey coloured shale in some parts of the study area This formation boundary coincides with that of the Tertiary/ Late Cretaceous The underlying Tor Formation con- ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at £$S- HIGH WSSm '• ">:::^ MID / N G E R M A N Y %, NORTH':':::V.-."\ i SEA HIGH j a m \ V x N ' ^ j * \ V DENMARK /I^ÄNETHERLANDSI CENTRA.! 'S'iJvSs-vÄ I KRABEN x ^_ LEGEND Chalk Field © High ^ Faults ~ ~ - Sector Delineation Fig 1: Location map, showing the main structural elements for the study area sists of chalky limestones of Maastrichtian to late Campanian age The Hod Formation underlies the Tor Formation and is predominantly early Campanian to Turonian in age This Formation was initially subdivided into three units by HARDMAN & EYNON (1977) and subsequent authors have revised the definition of these units For the purpose of this paper the subdivision follows the scheme developed by the author and used "in house" at Robertson Research International In this scheme the Hod Formation is divided into three units, the Upper, Middle and Lower Hod The Upper Hod is represented by chalky and quite clean limestones of early Campanian to Coniacian age and is of secondary importance as a reservoir The underlying Middle Hod Unit consists of limestone/marl alternations and is Coniacian to Turonian in age Finally the Lower Hod unit consists of quite pure chalky limestones (of secondary importance as a reservoir) but grades progressively into more argillaceous limestones towards the base of the Turonian The Lower Hod culminates in the grey to greenish grey Plenus Marl Formation of late Cenomanian age The underlying Hidra Formation of Cenomanian age consists of quite firm limestones which grade into the argillaceous limestones and calcareous clay145 ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at TIME (MILL YR.) BP CHRONOSTRATIGRAPHY oc o WO < GENERALISED LITHOSTRATIGRAPHIC NOMENCLATURE FORMATION LITHOLOGY TUFFMEOUS CLAYS TONE: Soft to fir«, medium dark grey, olive black non calcareous SHALE/CLAYSTOKi Dark grey to greenish grey, laminated, non calcareous Kith some tuFFaceous material a SHALE: medium grey to greenish grey non laminated, non calcareous LU CLAYSTPNEt Light grey, moderately t o highly calcareous, often grading into argillaceous limestones Frequently containing limestone c l e a t s of Late Cretaceous and Early Paleocene age -_y V_-_ :_V_rV _v_r LV_-^ p7H BALDER FORMATION SELE FORMATION LISTA FORMATION 31 O a > o 30 MAUREEN FORMATION EKOFISK FORMATION o c LU U I 3< < 60.2 LIMESTONE: Hard t o Moderately hard, medium light grey, s l i g h t l y argillaceous, grading into fairly s o f t , very light grey, highly calcareous chalks toward the base -r XI 0- UPPER LIMESTONE; Fir« »oderately chalky texture, white, very pale orange, grading into fir« brittle, platy, light grey, pinkish grey, locally pyritic limestones S II LOWER 73 UPPER LOWER LltESTONE: Fir», moderately to very chalky texture, Nhite to very light grey 83 LOWER m 87.5 'UPPER' LOWER' LOWER 91 UPPER LIMESTONE: Soft to firm, slightly chalky texture, white to very light grey grading into firm platy, light greenish grey, light grey, slightly to moderately argillaceous towards the base CLAYSTONE: Soft to firm medium dark grey to greenish grey locally waxy, non calcareous LIMESTONE: Firm, ldfcally chalky, white, becomes pale red with depth, slightly to moderately argillaceous Glauconite: as traces MIDDLE LOWER 97.5 O X > HOD FORMATION 30 O C "0 13 UPPER MIDDLE FORMATION xn i ü ii LIMESTONE: Fir» to soft , blocky t o platy aicrocrystalline, s l i g h t l y chalky, vrfiite to very light grey, argillaceouB, slightly pyritic 88.5- e TOR TRED m UPPER TZ in -rr a T= § r-LENÜt MAHL fOWMATKW Gl 3E RED HIDRA FORMATION =T- o CLAYSTONE: Firm, subfiasile, medium and medium dark grey, micronicaceous, moderately calcareous UPPER MIDDLE ARGILLACEOUS LIMESTONE: Firm, pale red argillaceous locally grading to calcareoua claystone CLAYSTONE OR SHALE: Dark grey micaceous, generally non calcareous with traces of pyrite R0DBY FORMATION 30 O 0Z aj m o=o SOLA FORMATION Fig 2: Generalised stratigraphy for the Upper Paleocene to Middle Albian interval for the southern Norwegian and Danish central graben area Lithostratigraphic nomenclature after DEEGEN & SCULL (1977) except for the Sola Formation which has been taken from HESJEDAL & HAMAR (1983) stones of the Rodby Formation of late Albian age The Hidra/Rodby Formation boundary coincides with the Upper/Lower Cretaceous boundary The middle Albian 146 ian to Aptian Sola Formation underlies the Rodby Formation and consists of non calcareous claystones or shales ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at Method of Investigations The investigations have been carried out using a Leitz Dialux 20 light microscope Centrifuge and smear slides were prepared followig the standard techniques described by TAYLOR & HAMILTON (1982) using core, sidewall core and in particular ditch cuttings samples The material examined and described in this paper is taken from released well sections and includes data from some of the Robertson Research International Limited multiclient reports in particular the report entitled "The Danish North Sea Area": The Stratigraphy and Petroleum Geochemistry of the Jurassic to Tertiary Sediments (1983), a report produced exclusively for the oil industry Since this paper is only a general review of the Upper Cretaceous calcareous nannofossil biostratigraphy from the study area and is predominantly based on ditch cuttings material, only stratigraphically significant abundances (i e acmes) are recorded These acmes are readily recognisable in this type of sample as well as core and sidewall core material The overall preservation of the nannofloral assemblages was noted but only characteristic nannofloral assemblage preservational horizons are documented (i e the very poorly preserved nannofloral assemblages characteristic of the middle to early Turonian age Lower Hod Unit) Calcareous Nannofossil Biostratigraphy 5.1 Previous Studies in Upper Cretaceous Calcareous Nannofossil Zonation morphotype of Kamptnerius magnificus by THIERSTEIN (1976) Arkhangelskiella ethmopora (Campanian) was also used as a zonal marker in this scheme but is considered to be a perforate morphotype of Arkhangelskiella cymbiformis Lithraphidites quadratus (Maastrichtian) was too inconsistently recorded to be a reliable zonal marker in the present study Subsequent authors have used some of CEPEK & HAY'S (1969) other zonal marker species in their schemes, such as Tetralithus aculeus (upper Campanian), subsequently used by MANIVIT (1971), VERBEEK (1976b), THIERSTEIN (1976), SISSINGH (1977), HAY (1977), PERCH-NIELSEN (1977, 1979a), ROTH (1978), PFLAUMANN & CEPEK (1982) and STRADNER & STEINMETZ (1984) This species was not recorded in the present study, neither was Corollithion exiguum (Turonian) which was used by MANIVIT (1971), ROTH (1973), BUKRY (1975), HAY (1977) as a zonal indicator The other two marker species used by CEPEK & HAY (1969), Chiastozygus cuneatus (Turonian / Cenomanian) and Chiastozygus initialis (Maastrichtian - Upper Campanian) were not noted in the study area 5.2 Historic reviews Authors and correlations: BUKRY & BRAMLETTE (1970) S t u d y a r e a : Leg of the Deep Sea Drilling Project from the South Atlantic A g e : Upper Cretaceous, Maastrichtian to Campanian interval Z o n e s : (3 of which were new) C o m m e n t s : Two zonal marker species used by these authors were found in the present study, namely Lithraphidites quadratus of Maastrichtian age which was rarely recorded and Eiffellithus angustus (= Eiffellithus eximius of this paper) of Campanian age which was found to have a very inconsistent top within the Campanian SISSINGH (1977) recorded this species as extending to within the early Maastrichtian interval at the Dyr el Kef Section in W Tunisia The other zonal marker species used by BUKRY & BRAMLETTE (op cit.) namely Tetralithus mums (= Micula murus of other authors) (late Maastrichtian) and Tetralithus nitidus (Maastrichtian - Campanian) were not found in the study area The former species has been used by subsequent authors to mark the top zone of the Maastrichtian in tropical and subtropical regions Figure illustrates diagrammatically the most important Upper Cretaceous calcareous nannofossil zonations proposed in the last twenty-two years The following section reviews these schemes and where possible in context of the one proposed in the present study The first subdivision of the Upper Cretaceous utilizing calcareous nannofossils was presented by STRADNER (1963) using assemblage zones Similar assemblage zonation schemes were proposed by STOVER (1966), REINHARDT (1966) and BUKRY (1969) However, it was not until 1969 that CEPEK & HAY introduced a zonation scheme for the Upper Cretaceous based on interval zones, using material from Kansas and Alabama SMITH (1975) pointed out that on reviewing the scheme and trying to assign the zones to stages, that at least some of Coniacian and Santonian interval had not been included in the original study conducted by CEPEK & HAY (1969) Three of the zones proposed by these authors A u t h o r a n d c o r r e l a t i o n s : MANIVIT (1971, 1972) have been identified and used in an emended form in S t u d y A r e a : France (including the stage stratotypes) this study, namely the Nephrolithus frequens zone (MaasA trichtian age in both studies), Tetralithus pyramidus g e : Tertiary-Cretaceous, Early Palaeocene to Aptian (= Quadrum gartneri zone of this study, Turonian in both interval Z o n e s : 15 of which 11 (1 of which was new) were for studies) and the Staurolithites orbiculofenestrus (= Axopodorhabdus albianus zone of this study, Cenoman- the Upper Cretaceous interval ian in both studies) zones Marthasterites furcatus and C o m m e n t s : A number of zones identified in this Kamptnerius magnificus are the only other zonal marker scheme were originally definded by CEPEK & HAY species introduced by CEPEK & HAY (op cit.) which (1969); MANIVIT however introduced the evolutionary were utilized in this study, although they have been asappearance of Gartnerago obliquus to define the base of signed a subzonal status in the Turonian This zonation the zone of the same name of predominantly scheme also used Kamptnerius punctatus (Campanian) as a Cenomanian age This zone has subsequently been zonal indicator which is considered a preservational used by THIERSTEIN (1974), VERBEEK (1976b, 1977), 147 ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at REINHARDT 1M6 CEPEK HAY, I, 1969 BUKRY, 1909 BUKRY I BRAMLETTE, 1970 MANIVIT, 1971, 1972 PERCH- RISATTI, BUKRY, 1873 1973b NIELSEN, 1972 a MISSISSIPPI, USA DSDP LEG 15, CARIBBEAN SEA BUKRY, 1974 & THIERSTEIN, 1974 DSDP LEO 17, CENTRAL PACIFIC BASIN DSDP LEG , INDIAN OCEAN BUKRY, VERBEEK 1975 1976b DSDP LEO , PACIFIC OCEAN TUNISIA, NORTH SISSINGH, 1977, 1978 TUNISIA, WESTERN EUROPE, TURKEY, OMAN & NEW JERSEY (USA) AFRICA ARKHANGELSKIELLA CVMBIFOHMIS REINHAHDTITES LEVIS QOTHICUS ASSOCIATION Fig 3: Comparison of Upper Cretaceous calcareous nannofossil zonation schemes HAY (1977), PERCH-NIELSEN (1977) and ROTH (1978) The evolutionary appearance of G obliquum was also noted by CRUX (1982), PFLAUMANN & CEPEK (1982) and STRADNER & STEINMETZ (1984) (?possibly) within the Cenomanian, although the former author mentions the difficulty as to whether to include rare small forms of Garnterago noted in the Cenomanian with this species and so did not use it as a zonal marker The evolutionary appearance of this species has not been used in this study although the stratigraphic extinction •has been used to define one of the zones of the same name in the Maastrichtian MANIVIT also used 148 Kamptnerius magnificus as zonal marker for the Santonian CEPEK & HAY (1969) used the evolutionary appearance of this species to mark the base of their zone in the Campanian The absence of Coniacian and Santonian age sediments in their study may explain this apparent discrepancy A modified form of this zone was subsequently used by THIERSTEIN (1974) (Turonian/Coniacian), HAY (1977) (Santonian) and ROTH (1978) (Turonian) In the present study it has been used as a subzonal marker species in the Turonian THIERSTEIN (1976) mentions that the first (last downhole) occurrence of Kamptnerius magnificus is ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at HAY, 1977 3VERVIEW AFTER MANIVIT, 1971 PERCHNIELSEN, 1977 LEG , WESTERN ATLANTIC OCEAN MANIVIT ETAL, 1977 GENERAL, INCLUDING NORTH WESTERN EUROPE AND VARIOUS DSDP LEGS VERBEEK, ROTH, 1977 1978 TUNISIA, SOUTHERN SPAIN AND FRANCE DSDP LEG 44, NORTH WESTERN ATLANTIC OCEAN PERCHNIELSEN & PRINS, 1979a A R E A BETWEEN THE NORTH SEA AND MEDITERRANEAN (ZONES AFTER BI88INQH 1977 1078} CRUX, SOUTHERN PFLAUMANN ft 1982 CEPEK, STRADNER WEST ENGLAND AFRICA ft THIS STEINMETZ, 1962 WORK 1904 NORTH WEST AFRICA SITE 930 OF THE DSDP NORTH SEA, SOUTHERN NORWEGIAN DANISH SECTORS First downhole occurrence Synchronous nannofossil events Last downhol« occurrence time-transgressive through at least my which may explain some of these age differences noted above A u t h o r and c o r r e l a t i o n s : PERCH-NIELSEN (1972) S t u d y a r e a :Leg 12 of the Deep Sea Drilling Project from the north Atlantic A g e : Upper Cretaceous, Maastrichtian interval Z o n e s : (2 of which were new) C o m m e n t s : Two new zones were introduced by PERCH-NIELSEN namely the Arkhangelskiella cymbiformis and Reinhardtites anthophorus (?/? levis of SISSINGH, 1977) zones If the top of the latter zone equates to the extinction level of Reinhardtites levis zone of SISSINGH (1977) then this zone has been recognised in the present study The Arkhangelskiella cymbiformis zone has been recorded in the present study but has been used in emended form to mark the uppermost Maastrichtian zone MARTINI (1976), SISSINGH (1977), PERCH-NIELSEN (1977) and STRADNER & STEINMETZ 149 ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at (1984) have all used this zone but for different intervals of the Maastrichtian parca and the extinction of Marthasterites furcatus whereas the latter zone encompasses the interval between the evolutionary appearances of Corollithion exiguum and Lithraphidites alatus and has subsequently been used by BUKRY (1974), THIERSTEIN (1974) and PERCH-NIELSEN A u t h o r a n d c o r r e l a t i o n s : RISATTI (1973) S t u d y a r e a : Mississippi, U S A A g e : Upper Cretaceous, Maastrichtian to Campanian interval Z o n e s : (6 of which were new) C o m m e n t s : Of the nine nannofloral zones recorded by the author, five were based on newly described species None of these species have since been noted outside this area The remaining three zones correspond to CEPEK & HAY'S (1969) scheme (1977) This species was only rarely recorded in the study area and therefore has not been used as zonal indicator A u t h o r a n d c o r r e l a t i o n s : BUKRY (1974) S t u d y a r e a : Leg 26 of the Deep Sea Drilling Project from the Indian Ocean A g e : Cretaceous, Maastrichtian to Berriasian interval Z o n e s : 18 of which 10 were for the Upper Cretaceous interval C o m m e n t s : The scheme was essentially based on the work of STRADNER, (1963), CEPEK & HAY (1969), A u t h o r a n d c o r r e l a t i o n s : BUKRY (1973b) S t u d y a r e a : Leg 15 of the Deep Sea Drilling Project ROTH (1973) and BUKRY (in press) However, THIERfrom the Caribbean Sea STEIN (1974) produced a slightly modified zonation scheme for Santonian to Albian interval of this Leg A g e : Upper Cretaceous, Maastrichtian to Campanian (See Figure for comparison) interval Z o n e s : (1 of which was new) C o m m e n t s : BUKRY introduced a Broinsonia parca zone (of Campanian age) and defined it as the interval between the evolutionary appearance of Tetralithus trifidus A u t h o r a n d c o r r e l a t i o n s : BUKRY (1975) (= Quadrum trifidum) and the extinction of Eiffellithus an-S t u d y a r e a : Leg 32 of the Deep Sea Drilling Project gustus (= E eximius of this paper) This zone has been from the Pacific Ocean used in emended form by VERBEEK (1976b, 1977), A g e : Cretaceous, Maastrichtian to Berriasian interval SISSINGH (1977), PERCH-NIELSEN (1977), ROTH (1978), Z o n e s : 18 of which 10 were for the Upper Cretaceous PERCH-NIELSEN & (PRINS, 1979a), CRUX (1982), interval PFLAUMANN & CEPEK (1982) and STRADNER & STEINMETZ (1984) The Broinsonia parca zone was used in theC o m m e n t s : BUKRY essentially followed the scheme present study but uses the stratigraphic extinction of proposed by ROTH (1973) with some minor modificathe species following the findings of SISSINGH (1977), tions who used this event to subdivide his Tranolithus phacelosus partial range zone 23 of earliest Maastrichtian to latest Campanian age into two subzones (23b and 23a) The scheme was otherwise identical to that A u t h o r a n d c o r r e l a t i o n s : VERBEEK (1976b) proposed by BUKRY & BRAMLETTE (1970) S t u d y a r e a : El Kef, Tunisia A g e : Upper Cretaceous, Maastrichtian to Cenomanian interval Z o n e s : 15 (of which were new) A u t h o r a n d c o r r e l a t i o n s : ROTH (1973) C o m m e n t s : This scheme was based exclusively on S t u d y a r e a : Leg 17 of the Deep Sea Drilling Project evolutionary appearances VERBEEK introduced Tetfrom the Central Pacific Ocean ralithus gothicus ( = Quadrum gothicum) as a zonal marker for the upper Campanian which has subsequently A g e : Upper Cretaceous, Maastrichtian to Cenomanian been used by PERCH-NIELSEN (1977), VERBEEK interval Z o n e s : 10 (2 of which were new) C o m m e n t s : VERBEEK (1976b) indicated that the scheme of ROTH has one main disadvantage in being based partially on extinctions which means it is difficult to recognise in samples with reworked material, however, the use of extinctions when dealing with ditch cuttings material is standard practice in the oil industry Many of the zones used by ROTH were proposed by earlier authors in particular BUKRY & BRAMLETTE (1970) and MANIVIT (1971) although this author defined two new zones; the Gartnerago obliquum and Lithraphidites alatus zones of Santonian and Cenomanian age respectively The former is based on the interval between the evolutionary appearance of Broinsonia 150 (1977), PFLAUMANN & CEPEK (1982) and STRADNER & STEINMETZ (1984) This species was not recorded in the present study However, two of the zones introduced by VERBEEK have been used in emended form in the present study the Zygodiscus spiralis zone of Santonian age (Maastrichtian in the current study) and the Eiffellithus eximius zone (Turonian age in both studies) The latter zone has been used by PERCHNIELSEN (& PRINS, 1979a) and CRUX (1982) for the Turonian and Turonian/ Conician interval respec- tively PFLAUMANN & CEPEK (1982) and STRADNER & STEINMETZ (1984), however, use a zone of this name in the lower Campanian ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at A u t h o r a n d c o r r e l a t i o n s : SISSINGH (1977) A g e : Coniacian to Albian interval S t u d y a r e a : Western Europe, Tunisia, Oman and Z o n e s : (one of which was new) and subzones New Jersey C o m m e n t s : Neither the new Lithraphidites acutum zone A g e : Cretaceous, Maastrichtian to Berriasian interval of early Turonian to Cenomanian age, or the Gartnerago obliquum, Cruciellipsis chiastia and Prediscosphaera spinosa Z o n e s : 26 of which 18 were for the Upper Cretaceous subzones of early Turonian to late Albian age could section (of which were new) together with 14 subbe recognised in the present study The Lithraphidites zones acutum zone has since been used by ROTH (1978) in C o m m e n t s : Three of SISSINGH'S new zones have emended form and STRADNER & STEINMETZ (1984) been adopted in the present study namely the Reinhardtites levis Zone 24, Tranolithus phacelosus CRUX (1982) used the species Lithraphidites acutum and (= Tranolithus orionatus of this study) Zone 23, both of Prediscosphaera spinosa on a subzonal level butemended early Maastrichtian age and the Lucianorhabdus cayeuxii both Zone 16 of late Santonian age A further three of his zones have been used on a subzonal status in emended form namely his Micula staurophora Zone 14 of Coniacian age, Marthasterites furcatus Zone 13 of Con-A u t h o r a n d c o r r e l a t i o n s : VERBEEK (1977) iacian age (Turonian age in the current study) and S t u d y a r e a : Tunisia, Southern Spain and France Tetralithus pyramidus (= Quadrum gartneri of this study) A g e : Cretaceous, Maastrichtian to Albian interval Zone 11, both of Turonian age Also his Subzone Z o n e s : 17 of which 16 (including new zone) were for 23a, the top of which is defined on the extinction of the Upper Cretaceous interval Aspidolithus ex gr parous (= Broinsonia parca of this study) was recognised in the present study but has C o m m e n t s : Although this zonation is similar to the been modified to zonal status As mentioned by CRUX one he introduced earlier (1976b) with some emend(1982), MANIVIT (1971) introduced the Micula staurophora ments, one new zone was proposed, the Rucinolithus zone but it differed from SISSINGH'S in that she probahayii zone of middle Santonian age This species, bly grouped Quadrum gartneri with Micula staurophora, however, was not recognised in the present study hence the confusion in the literature regarding the evolutionary appearance of these two species A more detailed comparison with SISSINGH'S zonation scheme is included later in the paper • A u t h o r a n d c o r r e l a t i o n s : ROTH (1978) S t u d y a r e a : Leg 44 of the Deep Sea Drilling Project from the North Western Atlantic Ocean A g e : Cretaceous, Maastrichtian to Berriasian interval A u t h o r a n d c o r r e l a t i o n s : HAY (1977) Z o n e s : 23 of which 13 (of which were new) were for S t u d y a r e a : None just an overview the Upper Cretaceous interval A g e : Cretaceous, Maastrichtian to Berriasian interval C o m m e n t s : ROTH discussed the Cretaceous calcareous nannofossil biostratigraphy in relationship to the Z o n e s : 19 of which 10 were for the Upper Cretaceous oceanic and classic European stages using the interval schemes of ROTH (1973), BUKRY (1975), THIERSTEIN C o m m e n t s : In a general review of calcareous nan(1976) and VERBEEK (1976) He proposed thirteen nofossils HAY essentially utilised the scheme prozones for the Upper Cretaceous and distinguished posed by MANIVIT (1971) with some minor modificathem by using the prefix NC and numbering them tions from 23 to 11 (youngest to oldest) Two new zones were introduced for the Upper Cretaceous namely the Lithraphidites praequadratus (NC 21 zone) of Maastrichtian age and the Tetralithus obscurus - Micula concava (NC 17 A u t h o r a n d c o r r e l a t i o n s : PERCH-NIELSEN (1977) zone) of ?Santonian age However the former S t u d y a r e a : Leg 39 of the Deep Sea Drilling Project species was not recorded in the present study and from the Western South Atlantic Ocean one of the latter zonal indicators Tetralithus obscurus A g e : Cretaceous, Maastrichtian to Albian interval (= Phanulithus obscurus of this paper) was found to have its last downhole occurrence at the Campanian / SanZ o n e s : 14 zones of which 13 were for the Upper Cretonian boundary which appears to be above ROTH'S taceous interval zone Micula concava was not recorded in this study C o m m e n t s : PERCH-NIELSEN emended several zones, but essentially followed the schemes of MARTINI (1969, 1976), CEPEK & HAY (1969), BUKRY & BRAMLETTE (1970), PERCH-NIELSEN (1972) and ROTH (1973) Authors and correlations: PERCH-NIELSEN (& PRINS, 1979a) A u t h o r a n d c o r r e l a t i o n s : MANIVIT et al (1977) S t u d y a r e a : North Western Europe and various DSDP Legs S t u d y a r e a : The area between the North Sea and the Mediterranean A g e : Cretaceous, Maastrichtian to Berriasian interval Z o n e s : 26 of which 18 were for the Upper Cretaceous section together with 14 subzones 151 ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at C o m m e n t s : These authors used the framework of the eighteen zones and fourteen subzones proposed by SISSINGH (1977) as the main basis of their zonation scheme but included some minor modifications and additional nannofloral events This zonation scheme is also compared in some detail to the one proposed in this paper owing to its relevance to the North Sea Basin Constraints of the Study In the preceeding section a review of the most important Upper Cretaceous calcareous nannofossil zonations proposed in the last twenty two years was presented Although the information contained within these schemes has been used, the following problems also had to be taken into account Ditch Cuttings Many of the samples examined in this study were A u t h o r a n d c o r r e l a t i o n s : CRUX (1982) ditch cuttings The use of ditch cuttings renders age dating by evolutionary appearances impractical beS t u d y a r e a : Southern England cause of the problems of caving and drilling mud conA g e : Upper Cretaceous, Campanian to Cenomanian tamination Since many Upper Cretaceous calcareous interval nannofossil zonation schemes rely on evolutionary apZ o n e s : (2 of which were new) and subzones pearances almost exclusively, it is very difficult to apply C o m m e n t s : CRUX (1982) recognised two new zones, any of these schemes directly to the study area the upper Campanian Prediscosphaera stoveri zone, and ROMEIN (1979) has noted that since calcareous nanan upper Coniacian to lower Santonian Lucianorhabdus nofossils are easily reworked the use of stratigraphic maleformis zone, together with two new Turonian sub- tops of species for zonal boundaries is highly undesirzones; the' Lucianorhabdus quadrifidus and Cylindralithus coronatus subzones, none of which were recognised in the present study CRUX also emended several other zones and although all the zones and subzones identified were defined on evolutionary appearances several of the zones have been modified and included in the present scheme but on a subzonal level Many of the species ranges definded by CRUX show great similarity to those recorded in this study A detailed comparison of this work has, therefore, been undertaken, because of its relatively close proximity to the study area, particularly in respect to the studies conducted to date by other authors Authors and correlations: PFLAUMANN & CEPEK (1982) S t u d y a r e a : North West African Continental Margin A g e : Cretaceous, Maastrichtian to Berriasian interval Z o n e s : 21 of which were for the Upper Cretaceous interval C o m m e n t s : PFLAUMANN & CEPEK produced a zonal scheme for the Upper Cretaceous consisting of nine zones essentially based on PERCH-NIELSEN'S (1977) zonation scheme with some modifications A u t h o r s a n d c o r r e l a t i o n s : STRADNER & STEINMETZ (1984) S t u d y a r e a : Site 530 of the Deep Sea Drilling Project, Angola Basin A g e : Cretaceous, Maastrichtian to Albian interval Z o n e s : 11 (1 of which was new) able However, in the oil industry this is the only practical method to date rocks from cuttings, although this limitation cannot be overlooked 6.2 Type of Drilling In suitably aged turbo drilled well sections nannofossils are often the only means to date the material Since the nannofossils recovered from samples from this type of drilling are frequently fragments this renders identification difficult unless the species is both robust and readily identifiable These two parameters characterise the forms chosen as zonal markers in this paper 6.3 Diagnostic Species Many of the diagnostic species used in previous zonation schemes were not recorded in the present study Many of the forms which were recorded in this study were employed in previous schemes as zonal markers, on the basis of evolutionary appearances and not stratigraphic tops 6.4 Preservation In general the nannofloral assemblages from the Upper Cretaceous chalks of the study area are quite poorly preserved As a direct result of this, only the more dissolution resistant and robust forms were noted consistently in most well sections This renders the use of delicate and dissolution prone species impractical as zonal or subzonal markers in a study conducted on this type of material On a more local scale where preservation is more suitable, they can be used to confirm age dating and provide additional biostratigraphic datums C o m m e n t s : STRADNER & STEINMETZ adopted the zo- nation scheme used by PFLAUMANN & CEPEK (1982) However, they did introduce a new late Turonian 6.5 Geological Structure zone, based on a new species, namely Liliasterites anSince many of the oil well sections analysed in the gularis This species, however, was not recorded in present study are drilled on structural highs, the matethe present study 152 ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at es not d rawn to sca e n9e of sp.cies ( in ihis »ort ) straligraphic downhole sl'altgraphic downhole Encarta i cfkno» Rel • f! live Abundances • Abundant [=^ M i d uals m s a c h leid ol • Common [ ^ ind idu 10 ields ol pr.„m ( = t »dl idu«l in „ o h 100 li.lds o -10 ,n , o h Fig 6: Range chart showing distribution of selected important calcareous nannofossil species recorded in the Hod Formation thyan influence (which may in itself explain their abA g e : Late Santonian sence) The base of this subzone is defined on the L i t h o s t r a t i g r a p h i c U n i t : Hod Formation (Upper last downhole occurrence of Phanulithus obscurus follow- Hod Unit [part]) ing SISSINGH (1977), although, this event was correL a s t o c c u r r e n c e s ( b a s e s ) : Lucianorhabdus cayeuxii lated to the upper Santonian by PERCH-NIELSEN (& and Arkhangelskiella cymbiforrnis PRINS, 1979a) CRUX (1982) did not recognise this event and indicated that Phanulithus obscurus was dif- R e m a r k s : SISSINGH (1977) indicated that his Zone 16 is solely of late Santonian age, with its upper limit ficult to separate from Phanulithus ovalis in material corresponding to the Campanian/Santonian boundary which had undergone overgrowth cementation and PERCH-NIELSEN (& PRINS, 1979a, p 227) correlate this suggested that the last downhole occurrence of this boundary to the 17/18 boundary of SISSINGH (1977), a species might be as low as the Turonian For the purboundary which is delimited by the last downhole ocpose of this study the last downhole occurrence of Phanulithus obscurus is taken to approximate the bound- currence of Aspidolithus sp (after PRINS, 1977) ary between the Campanian suggested by SISSINGH (1977) and Santonian as CRUX'S (1982) Lucianorhabdus cayeuxii zone straddles the Campanian/Santonian boundary and utilises the last downhole occurrence of Broinsonia parca to mark the top within the lower Campanian For the purpose of 7.2.2.2.2 Lucianorhabdus cayeuxii this paper the findings of SISSINGH (1977) seem to be Partial Range Subzone NK12B most applicable to the present study PERCH-NIELSEN A u t h o r : SISSINGH (1977) Equates with Zone 16 of SIS(& PRINS, 1979a) noted the first downhole occurrence SINGH (1977) as defined by PERCH-NIELSEN & PRINS of Lithastrinus floralis at the boundary between Zones 17 (1979a) and the Lucianorhabdus cayeuxii zone (part) of and 16 of SISSINGH (1977) In the present study this CRUX (1982) species was recorded towards the base of this subzone CRUX (1982) noted the first downhole occurD e f i n i t i o n : Interval from the last downhole occurrence of Phanulithus obscurus to the last downhole oc- rence of Lithastrinus floralis within the upper Santonian which is similar to the findings of PERCH-NIELSEN (& currence of Lucianorhabdus cayeuxii 161 ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at PRINS, 1979a) and also Actinosphaera deflandrei, this latter species was not recorded in the present study He also attached importance to Rucinolithus sp (an 8rayed form whose rays radiate with only slight inclination and imbrication) This species appeared to have a last downhole occurrence within the upper Santonian Cylindralithus sp CRUX (1982) (a species defined as having no central cross with a complex rim and flaring distal cylinder, composed of several overlapping cycles of irregular elements) has its last downhole occurrence towards the base of his Lucianorhabdus cayeuxii zone CRUX (1982) noted that this species can be difficult to distinguish from Cylindralithus biarcus under the light microscope These latter three species were not observed in the present study This author (1982) also indicated the last downhole occurrence of Arkhangelskiella cymbiformis within the Santonian, an o b - servation confirmed in the present study and men- are recorded A distinctive foraminiferal change is also noted at this boundary with assemblages dominated by Globotruncana spp This contrasts with the very sparse and poorly preserved nannofloral assemblages noted in the overlying Santonian interval The marked change at this boundary may reflect a change in environmental conditions HATTNER et al (1980) indicated that the dominance of such species as Gartnerago obliquum is more characteristic of nearshore assemblages, suggesting a shallowing of water depth over this interval The abundance of Watznaueria barnesae is also almost certainly related to environmental parameters NK13 Zone can be subdivided into four subzones; these are described and discussed below, although most of them are of secondary importance because they are defined on stratigraphic bases This assemblage zone is of very variable thickness in the study area tioned that the occurrence of Arkhangelskiella cymbiformis in much older sediments than previously recorded can be explained by inclusion of forms usually distinguished as Arkhangelskiella specillata in Arkhangelskiella cym- biformis CRUX regarded these two species as preservational morphotypes, a conclusion supported by this study The nannofloral assemblages recorded from this zone tend to be very poorly preserved 7.2.2.3 Watznaueria barnesae Assemblage Zone NK 13 A u t h o r : MORTIMER (this work) Equates to Zones 15, 14, 13 and 12 (part) of SISSINGH (1977), Zones 15, 7.2.2.3.1 Ahmuellerella octoradiata Interval Range Subzone NK 13A A u t h o r : MORTIMER (this work) Equates to Zones 15 and 14 of SISSINGH (1977) and PERCH-NIELSEN (& PRINS, 1979a) and the Lucianorhabdus cayeuxii (part) Reinhardtites anthophorus and Lucianorhabdus maleformis (part) zones of CRUX (1982) D e f i n i t i o n : Interval from the first downhole occurrence of common/abundant Watznaueria barnesae to the first downhole occurrence of common/abundant Eiffellithus eximius A g e : Early Santonian 14, 13 of SISSINGH (1977) as defined by PERCHL i t h o s t r a t i g r a p h i c U n i t : Hod Formation (Upper NIELSEN (& PRINS, 1979a); the Lucianorhabdus cayeuxii Hod Unit [part]) (part) Reinhardtites anthophorus, Lucianorhabdus maleformis, F i r s t a p p e a r a n c e ( t o p ) : Lithastrinus floralis Micula staurophora and Eiffellithus eximius (part) zones of CRUX (1982) Last o c c u r r e n c e ( b a s e s ) : and Orastrum campanensis Reinhardtites anthophorus D e f i n i t i o n : Interval from the first downhole occurrence of common/abundant Watznaueria barnesae or theR e m a r k s : SISSINGH (1977) noted the last downhole last downhole occurrence of Lucianorhabdus cayeuxii to occurrence of Reinhardtites anthophorus which he used to define the base of the zone of the same name as did the first downhole occurrence of common/abundant PERCH-NIELSEN (& PRINS, 1979a) and CRUX (1982) helicolithus valhallensis (MORTIMER n sp in prep, see which all equate in part to subzone NK 13A PERCHbrief notes in Taxonomy, Appendix I) NIELSEN (& PRINS, 1979a) recognised additional A g e : Early Santonian - Conacian marker species to delimit the base of SISSINGH'S Zone L i t h o s t r a t i g r a p h i c U n i t : Hod Formation (Upper 15 namely Lithastrinus grillii and Micula concava Neither [part] and Middle [part] Hod Units) of these species were recorded in the present study For information on the various first and last downhole CRUX (1982) noted the last downhole occurrence of occurrences of the specieß in this zone, refer to the Reinhardtites minimus and Ahmuellerella regularis within the individual subzone sections lower Santonian In the present study Ahmuellerella regularis was found to have its last downhole occurrence D i s c u s s i o n : The Santonian part of this zone is within the Campanian, and Reinhardtites minimus was marked by very impoverished and poorly preserved only rarely recorded in the study area CRUX (1982) nannofloral assemblages (due in part to the relatively also indicated the last downhole occurrence of hard nature of the limestone lithologies of the Upper Lucianorhabdus cayeuxii below that noted by SISSINGH Hod Unit) The top of this zone is marked by a notice(1977) In this paper the last downhole occurrence of able and distinctive increase in the numbers of Watznaueria barnesae which coincides closely, in suitable Lucianorhabdus cayeuxii is taken to approximate to the late/early Santonian boundary following the findings sections, with the last downhole occurrence of Lucianorhabdus cayeuxii and is taken to approximate the of SISSINGH (1977) upper/lower Santonian boundary for the purpose of CRUX (1982) indicated that his Lucianorhabdus maleformis this study The Coniacian/Santonian boundary is zone is of early Santonian - late Coniacian age almarked by a distinctive nannofloral break in the study though, on p 108 table 5.3 the Lucianorhabdus maleforarea and the North Sea Basin in general mis zone appears to be restricted to the lower SantonBelow the boundary moderately preserved and relaian which contradicts his original statement about the tively rich nannofloral assemblages which are domiage of the zone (page 94) In view of this it is difficult nated by Watznaueria barnesae and to a lesser extent Eif- to equate this zone to Subzone NK 13A For the purfellithus eximius, Gartnerago obliquum and Tranolithus orionatus pose of this paper it is taken as it appears in the text 162 ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at which ranged well into the Turonian This is almost certainly due to the grouping of specimens of Quadrum gartneri with Micula staurophora, which would explain this A u t h o r : MORTIMER (this work) Equates with Zone 14 apparent discrepancy SISSINGH (1977) defined his (part) of SISSINGH (1977) and PERCH-NIELSEN (& Zone 14 as the interval between the last downhole PRINS, 1979a) and the Lucianorhabdus maleformis zone occurrence of Reinhardtites anthophorus and the last (part) of CRUX (1982) downhole occurrence of Micula ex gr staurophora of late D e f i n i t i o n : Interval between the appearance of comConiacian to early Santonian age PERCH-NIELSEN (& mon/abundant Eilfellithus eximius to the first downhole PRINS, 1979a) and SISSINGH (1977) identified the occurrence of Helicolithus valhallensis (MORTIMER n sp same zone and placed the lower boundary at the late/ in prep, see Appendix I, Taxonomy for brief descripearly Coniacian boundary CRUX (1982) however, detion) fined his Micula staurophora zone as the interval between the last downhole occurrence of Lucianorhabdus A g e : Late Coniacian maleformis and Micula staurophora of middle Coniacian L i t h o s t r a t i g r a p h i c U n i t : Hod Formation (Upper age and showed it equating to Zone 13 (part) of SIS[part] to Middle [part] Hod Units) SINGH (1977) which makes exact comparisons difF i r s t a p p e a r a n c e s ( t o p s ) : Lithastrinus moratus and ficult For the purpose of this paper the base of SubMarthasterites furcatus zone NK 13C is approximated to the late/early ConR e m a r k s : CRUX (1982) noted the first downhole ociacian boundary currence of Marthasterites furcatus and Quadrum gartneri subsp towards the top of the Coniacian This latter 7.2.2.3.4 Prediscosphaera cretacea species was diagnosed by CRUX (1982) as a subInterval Range Subzone NK 13D species of Quadrum gartneri which is composed of two A u t h o r : MORTIMER (this paper) (non THIERSTEIN 1971 layers each consisting of four blocks of calcite sepaand 1973) Equates with Zones 13 and 12 (part) of rated by sutures, the blocks are distorted rectangles SISSINGH (1977); Zone 13 of SISSINGH (1977) as dein plan view and are arranged in an approximate square In this study Marthasterites furcatus occurs to- fined by PERCH-NIELSEN (& PRINS, 1979a); the Micula staurophora zone (part) and Eiffelithus eximius zone of wards the top of the upper Coniacian which agrees CRUX (1982) with the findings of CRUX The species is known to occur in younger sediments elsewhere; SISSINGH D e f i n i t i o n : Interval between the last downhole oc(1977) and PERCH-NIELSEN (& PRINS, 1979a) show currence of Micula staurophora to the first downhole apthis event as occurring within the early Campanian at pearance of common/abundant Helicolithus valhallensis the top of Zone 18 of these authors In the study area (MORTIMER n sp in prep, see Appendix I on Marthasterites furcatus can be used to indicate the pene- Taxonomy for brief description) tration of Coniacian age sediments One explanation A g e : Early Coniacian for the relatively restricted occurrence of this species L i t h o s t r a t i g r a p h i c U n i t : Hod Formation (Middle in the North Sea Basin could be because of the geneHod Unit [part]) rally higher argillaceous content of the Coniacian and R e m a r k s : PERCH-NIELSEN (& PRINS, 1979a) note the uppermost Turonian chalks These in turn yield better last downhole occurrence of Lithastrinus septenarius as preserved and richer nannofloral assemblages comoccurring within Zone 13 of SISSINGH (1977) Howpared to the Santonian and late Turonian age chalks above and below CRUX'S Quadrum gartneri subsp has ever, this species was not recorded in the present study CRUX (1982) records the last downhole occurronly an inferred range in the latest Coniacian, and ences of Lithastrinus grilli and Lucianorhabdus arcuatus towas not distinguished from Quadrum gartneri in this wards the top of the Micula staurophora zone which study equates in part with Subzone NK 13D, although neither of these species were recorded in the present study (see Remarks under Subzone NK14A for 7.2.2.3.3 Micula staurophora further discussion of the earliest Coniacian to latest Partial Range Subzone NK 13C Turonian interval) A u t h o r : SISSINGH (1977), emended MORTIMER (this paper) (non MANIVIT, 1971) Equates with Zone 14 7.2.2.3.2 Lithastrinus moratus Interval Range Subzone NK 13B (part) of SISSINGH (1977) and PERCH-NIELSEN (& PRINS, 1979a); the Lucianorhabdus maleformis zone (part) 7.2.2.4 Helicolithus valhallensis of CRUX (1982) Assemblage Zone NK 14 D e f i n i t i o n : Interval from the first downhole occurA u t h o r : MORTIMER (this paper) Equates to Zones 12 rence of Helicolithus valhallensis (MORTIMER n sp in prep, (part) and 11 (part) of SISSINGH (1978) and Zones 12 see Taxonomy in Appendix I for brief description) to and 11 (part) of SISSINGH (1977) as indicated by the last downhole occurrence of Micula staurophora PERCH-NIELSEN (& PRINS, 1979a); the Eiffellithus eximius A g e : Late Coniacian (part) and Quadrum gartneri subsp (part) Zones and L i t h o s t r a t i g r a p h i c U n i t : Hod Formation (Middle Lucianorhabdus quadrifidus and Cylindralithus coronatus (part) Hod Unit [part]) subzones of CRUX (1982) F i r s t a p p e a r a n c e ( t o p ) : Helicolithus valhallensis (MOR- D e f i n i t i o n : The interval from the first downhole ocTIMER n sp in prep.) currence of abundant/common Helicolithus valhallensis (MORTIMER in prep.) to the first downhole appearance L a s t o c c u r r e n c e ( b a s e ) : Micula staurophora of common/abundant Lithastrinus spp R e m a r k s : MANIVIT (1971) and THIERSTEIN (1976) used Micula staurophora to define a zone of the same name A g e : Turonian 163 ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at (MORTIMER in prep.) to the last downhole occurrence L i t h o s t r a t i g r a p h i c U n i t : Hod Formation (Middle of Marthasterites furcatus [part] and Lower Hod Units) For information on the first and last occurrences of A g e : Late Turonian species in this zone, refer to the relevant subzone deL i t h o s t r a t i g r a p h i c U n i t : Hod Formation (Middle scriptions and Fig Hod Unit [part]) D i s c u s s i o n : The Coniacian/Turonian boundary apL a s t o c c u r r e n c e ( b a s e ) : Marthasterites furcatus pears to be located within a section comprising relaR e m a r k : The Marthasterites furcatus zone was introduced tively argillaceous chalks This is based on the disby CEPEK & HAY ()1969) who defined it as the interval tinctive increase in number of Helicolithus valhallensis from the last downhole occurrence of Arkhangelskiella which occurs within this unit and for the purpose of ethmopora to the last downhole occurrence of Marthasterthis paper is taken to approximate with this boundary ites furcatus of Campanian age SMITH (1975) indicated The exact dating of this event is difficult because of that a stratigraphical interval covering at least part of the almost complete lack of foraminiferal control and the Santonian to Coniacian interval was not covered in part nannofloral data over this interval From exin their study Since then numerous revisions to the trapolation of available nannofloral data above and position of the upper boundary of this zone have below this event an approximate age can be assigned been put forward including MANIVIT (1971), ROTH to this feature Micula staurophora occurs above this (1973), BUKRY (1975), VERBEEK (1976) and HAY event in the study area and has a reported last down(1977) all utilising different species to define the hole occurrence within the Coniacian SISSINGH upper limit of this zone SISSINGH (1977), PERCH(1977) and PERCH-NIELSEN (& PRINS, 1979a) used it NIELSEN (& PRINS, 1979a) defined their Marthasterites to define their late/early Coniacian boundary CRUX furcatus Zone 13 as the interval between the last (1982) placed the same event within the middle Condownhole occurrence of Micula ex gr staurophora to the iacian, and indicates that sediments of definite Conlast downhole occurrence of Marthasterites furcatus of iacian age occur above this event (probably of the early Coniacian age PERCH-NIELSEN (& PRINS 1979a) lower part based on the work of the authors mencorreleated the base of this zone to the Coniacian/ tioned above) Marthasterites furcatus appeared to have a Turonian boundary This correlation agrees with the last downhole occurrence just below (approx 10 m) studies of THIERSTEIN (1976), VERBEEK (1976), this feature in the study area This species was used by SISSINGH (1977) and PERCH-NIELSEN (& PRINS, 1979a) to approximate the Coniacian/Turonian boundary CRUX (op cit.) indicated that Marthasterites furcatus although rare in his study was recorded within the Turonian of Southern England If this latter line of evidence is followed the Helicolithus valhallensis event must lie in quite close proximity to the Coniacian/ Turonian boundary Even if the evidence of SISSINGH (1977) and PERCH-NIELSEN (1979a) is followed then this event is still close to the boundary It must be emphasised that the approximation of this feature to this boundary is important since otherwise no clear distinction between Coniacian and Turonian age sediments would be possible, both in the study area and the North Sea Chalk province in general Nannofloral preservation and recovery deteriorates markedly on penetration of the Lower Hod Unit, due to the very clean and relatively hard nature of the chalks which characterise this unit This has resulted in great difficulty in confidently further subdividing the Turonian interval on the basis of calcareous nannofossils Towards the base of the Lower Hod Unit, however, a marked increase in the argillaceous content of the chalks is recognised (resulting in a slight improvement in nannofloral recovery and preservation) Four subzones can be recognised covering the NK 14 zone These are described and discussed below They are however, of secondary importance since they utilise stratigraphic bases of species 7.2.2.4.1 Marthasterites furcatus Concurrent Range Subzone NK 14A A u t h o r s : CEPEK & HAY (1969) emended MORTIMER (this paper) Equates Zone 12 (part) of SISSINGH (1977) and PERCH-NIELSEN (& PRINS, 1979a); the Eif- PERCH-NIELSEN (1977), ROTH (1978), CEPEK & PFLAU- MANN (1982) and STRADNER & STEINMETZ (1984), all of whom accept that this well documented worldwide event approximates to the stage boundary In contrast, STRADNER (1963) and CRUX (1982) reported Marthasterites furcatus from within Turonian age sediments According to STRADNER & STEINMETZ (1984, p 570) the forms attributed to Marthasterites furcatus should in fact be included in the older genus Liliasterites However, CRUX'S photograph on pi 22, pi 5.5 Fig 13 is clearly Marthasterites furcatus, thus the conclusion of this author, that the form ranges into the upper Turonian has been followed in the present study The main limitation for use of this species is that it is being used as a stratigraphic base and its upper occurrence is apparently partly if not wholly controlled by the lithological nature of the chalk For localised use, however, it appears to be a useful correlative event CRUX (1982) indicated that his Eiftellithus eximius zone encompassed the lower Coniacian to middle Turonian section (based on the interval between the last downhole occurrence of Micula staurophora to the last downhole occurrence of Eiftellithus eximius CRUX recorded the first downhole occurrence of Cylindralithus coronatus within the upper part of this zone, although THIERSTEIN (1976) noted that this species is easily destroyed by dissolution (which may explain its absence from the study area) 7.2.2.4.2 Kamptnerius magnificus Partial Range Subzone NK 14B A u t h o r : ROTH (1978) Probably equates to Zone 12 (part) of SISSINGH (1977) and PERCH-NIELSEN (& PRINS, 1979a) and the Eiftellithus eximius zone (part) of CRUX (1982) fellithus eximius zone (part) of CRUX (1982) Definition: Interval from the last downhole ocurD e f i n i t i o n : Interval from the first downhole occurrence of Marthasterites furcatus to the last downhole ocrence of common/abundant Helicolithus valhallensis currence of Kamptnerius magnificus 164 ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at satisfactory for purpose of the oil industry but no A g e : Late - Middle Turonian other age diagnostic taxa were recorded within the L i t h o s t r a t i g r a p h i c U n i t : Hod Formation (Middle Lower Hod Unit CRUX (1982) noted that Parhabdolithus Hod Unit [part]) achlyostaurion, Axopodorhabdus dietzmannii, Staurolithites crux, Last occurrence ( b a s e ) : Kamptnerius magnificus Helicolithus bifarius, Tranolithus salillum, Flabellites oblonga R e m a r k s : SISSINGH (1977) used the last downhole ocand Corollithion Signum all have their first downhole occurrence of Lucianorhabdus maleformis to define the base currences within the lower part of his Eiffellithus eximius of his Zone 12 which straddles the Coniacian/Turozone (which equates in part to Subzone NK 14C of nian boundary PERCH-NIELSEN (& PRINS, 1979a) used this study) None of these species were found to have the last downhole occurrence of Eiffelithus eximius to first downhole occurrences within this zone, which define the lower limit of SISSINGH'S Zone 12, as did can probably be explained partly by the unsuitable CRUX (1982) to define his Eiffellithus eximius zone CRUX nature of the lithology for good nannofloral recovery also recognised a number of species which have their Parhabdolithus achlyostaurion and Axopodorhabdus dietzmannii last downhole occurrence within the upper Turonian were found to have their first downhole occurrences i e Reinhardtites biperforatus, Marthasterites furcatus, Quadrum lower in the section and Tranolithus salillum was felt to gartneri subsp and Phanulithus obscurus In the present be a very unreliable marker Helicolithus bifarius, Corolstudy only Marthasterites furcatus was found to have its lithion Signum and Staurolithites crux were only rarely relast downhole occurrence close to the Turonian/Concorded in the study and hence no biostratigraphic sigiacian boundary No subdivision of Quadrum gartneri into nificance was attached to them subspecies was attempted and the last downhole occurrences of Reinhardtites biperforatus and Phanulithus obscurus were not observed within the Turonian of the 7.2.2.4.4 Quadrum gartneri study area The use of the last downhole occurrence Partial Range Subzone NK 14D of Kamptnerius magnificus for delimiting the base of the A u t h o r s : CEPEK & HAY (1969) (Tetralithus pyramidus), subzone of the same name was found to be fairly reliemended MANIVIT et al (1977) Equates to Zone 11 able in the study area However, CRUX (1982) indi(part) of SISSINGH (1978) and Zone 11 of SISSINGH cated that Kamptnerius magnificus has a last downhole (1977) as defined by PERCH-NIELSEN (& PRINS, occurrence within his Quadrum gartneri subsp zone 1979a); the Quadrum gartneri subsp zone (part), the of middle to early Turonian age It is, therefore, quite Lucianorhabdus quadrifidus (part) and Cylindralithus coronatus likely that the presence of Kamptnerius magnificus may be (part) subzones of CRUX (1982) controlled by lithology (i e.it is absent in the hard D e f i n i t i o n : Interval from the last downhole occurlimestones of the Lower Hod Unit (upper part) which rence of Eiffellithus eximius to the last downhole occurwould make this species use as a marker species rence of Quadrum gartneri and / or the first downhole ocvery unreliable on a regional level The occurrences currence of common/abundant Lithastrinus spp of the hard platy limestones of the Lower Hod Unit A g e : Early Turonian however, are widespread in the study area and it is felt that this form can be used on a relatively local L i t h o s t r a t i g r a p h i c U n i t : Hod Formation (Lower basis in the absence of any other species to mark the Hod Unit [part]) second subzone of the Turonian THIERSTEIN (1976) Last o c c u r r e n c e ( b a s e ) : Quadrum gartneri noted that the first occurrence of Kamptnerius magnificus R e m a r k s : SISSINGH (1977) indicated that his Tetralithus is time-transgressive through at least my and that it pyramidus (= Quadrum gartneri of this study) zone may preferred cooler water temperatures which may exrange into the late Cenomanian (latest part), although plain this apparent discrepancy in the range of this he considered that the zone was essentially early species noted by various authors Turonian in age (a view that has been followed in the present study) PERCH-NIELSEN (& PRINS, 1979a) and CRUX (1982, p 92) clearly showed the last downhole 7.2.2.4.3 Eiffellithus eximius occurrence of his Quadrum gartneri subsp (defined as Partial Range Subzone NK 14C early forms whose elements in plan view show a disA u t h o r : VERBEEK (1976) emended MORTIMER (this torted square shape so that the corners of the cube work, non ROTH, 1973) Probably equates with radiate outwards) delimits the Turonian/Cenomanian Zones 11 (part) and 12 (part) of SISSINGH (1977) and boundary This author also noted that Helicolithus anPERCH-NIELSEN (& PRINS, 1979a) and the Eiffellithus ceps, Kamptnerius magnificus, Ahmuellerella octoradiata and eximius (part) and Quadrum gartneri subsp (part) zones Lucianorhabdus quadrifidus all have their first downhole and Lucianorhabdus quadrifidus subzone (part) of CRUX occurrences and Octocyclus reinhardtii its first downhole (1982) occurrence within the Quadrum gartneri subsp zone Lucianorhabdus quadrifidus was not recorded and D e f i n i t i o n : Interval from the last downhole occurrence of Kamptnerius magnificus to the last downhole oc- Kamptnerius magnificus, Ahmuellerella octoradiata and Helicolithus anceps were found to have higher last downcurrence of Eiffellithus eximius hole occurrences in the Turonian than reported by Last a p p e a r a n c e ( b a s e ) : Ahmuellerella octoradiata A g e : Middle Turonian L i t h o s t r a t i g r a p h i c U n i t : Hod Formation (Lower Hod Unit [part]) R e m a r k s : Very impoverished and poorly preserved nannofloral assemblages were recorded from this subzone The use of stratigraphic bases to define the upper and lower boundaries of this subzone is un- CRUX 7.2.2.5 Lithastrinus spp Assemblage Zone NK 15 A u t h o r : MORTIMER (this work) (also see remarks) D e f i n i t i o n : The interval from the first downhole occurrence of common/abundant Lithastrinus spp includ165 ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at ing Lithastrinus floral is (9 rays), Lithastrinus moratus (7 rays) occurrence of this zone at the base of the Turonian is and Lithastrinus sp (8 rays) to the appearance of genalmost certainly related to environmental and / or lithological constraints, i e the increase in argillaceerally non calcareous dark to greenish grey shales of ous content of the Lower Hod Formation over this inthe Plenus Marl Formation terval CRUX (1982) noted that the first downhole ocA g e : Early Turonian currence of Octocyclus reinhardtii is within the Early L i t h o s t r a t i g r a p h i c U n i t : Hod Formation (Lower Turonian This species was found to have its first Hod Unit [part]) downhole occurrence within the Late Cenomanian in F i r s t a p p e a r a n c e ( t o p ) : Parhabdolithus achlyostaurion this study Helicolithus valhallensis has its last downhole Last o c c u r r e n c e ( b a s e ) : Helicolithus valhallensis occurrence towards the base of this subzone and (MORTIMER in prep.) Parhabdolithus achlyostaurion has its first downhole occurrence within this subzone in the study area R e m a r k s : Difficulties have arisen in accurately equating zone NK15 to the zonal schemes of SISSINGH (1977), PERCH-NIELSEN (& PRINS, 1979a) and CRUX 7.2.3 Plenus Marl Formation (Late Cenomanian age) (1982) (see remarks also in NK 14D) Since the stratigraphic position of this zone is just above the Plenus Marl Formation (the definition of which for the purpose of this paper follows that of the Geological Society London Special Report No on the Cretaceous) its recognition is considered to indicate penetration of earliest Turonian sediments It may be considered to possibly equate to the basal part of Zone 11 The Cenomanian/Turonian boundary for the purpose of this paper is taken to coincide with the lithological boundary between the Hod and Plenus Marl Formations This conclusion follows the Geological Society of London Special Report No on the Cretaceous which places the Cenomanian/Turonian boundary just above of SISSINGH (1977) and PERCH-NIELSEN (& PRINS, the Plenus Marl at the top of the gracile ammonite zone 1979a) and CRUX'S Quadrum gartneri subsp zone The based on studies from both onshore and offshore B Species I Full range of species T i not drawn to scale C in this work ) First stratigraphic downhole occurrence known , tast downhole occurrence uncertain First stratigraphic downhole occurrence uncertain , last downhole occurrence known Relative Abundances : | f • Abundanl C=^ • Common [ ^ individual O Present ( ^ individual -10 individuals in each in each 10 in each 100 ield of view ) ields fields of view ) of view Fig 7: Range chart showing distribution of selected important calcareous nannofossil species recorded in the Plenus Marl, Hidra and Robdy Formations 166 ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at L i t h o s t r a t i g r a p h i c U n i t : Hidra Formation (upper part) F i r s t a p p e a r a n c e s ( t o p s ) : Microstaurus chiastius, Reinhardtites fenestratus and Axopodorhabdus albianus R e m a r k s : ROTH (1978) introduced the Axopodorhabdus 7.2.3.1 Barren / Impoverished Zone albianus NC zone defined as the interval between the A u t h o r : MORTIMER (this work) Equates to Zone 10 last downhole occurrence of Eiffellithus turriseiffelii to the (part) of SISSINGH (1977) and PERCH-NIELSEN (& last downhole occurrence of Axopodorhabdus albianus of PRINS, 1979a), the Eiffellithus turriseiffeli zone (part) and Albian age In the present study the extinction of Microrhabdulus decoratus subzone (part) of CRUX (1982) Axopodorhabdus albianus has been employed to define the top of the zone of the same name of late D e f i n i t i o n : Interval between the outgoing of common/ Cenomanian age The nannofloral assemblages abundant Lithastrinus spp and the first downhole ocwithin this zone are dominated by Tranolithus orionatus currence of Axopodorhabdus albianus and Broinsonia enormis, a species association which on A g e : Late Cenomanian a local basis can be used to indicate the penetration L i t h o s t r a t i g r a p h i c U n i t : Plenus Marl Formation of late Cenomanian age deposits in the absence of R e m a r k s : This zone is characteristically barren of calany of the characteristic marker species for delimiting careous nannofossils or occasionally yields very imthis zone The abundance of the latter species may poverished nannofloral assemblages containing only suggest a shallowing during the deposition of the dissolution resistant species such as Watznaueria bar- Hidra Formation (HATTNER et al [1980] noted an innesae The present author has recorded moderately dicrease in the relative abundance of Broinsonia in nearverse nannofloral assemblages from the Plenus Marl shore nannofloral assemblages) CRUX (1982) of Lincolnshire (paper in prep.) CRUX (1982) noted showed the first downhole occurrence of Microstaurus Axopodorhabdus albianus, Microstaurus, chiastius and Crechiastius, Cretarhabdus striatus, Lithraphidites acutum and the tarhabdus striatus as having extinctions close to the last downhole occurrence of Zygodiscus minimus within Turonian / Cenomanian boundary in Southern Engthe upper part of his Eiffellithus turriseiffelii zone (which land Two of these species were recorded in the precorresponds in part to the NK 16 zone of this study) sent study as having their first downhole occurrence Microstaurus chiastius, and Axopodorhabdus albianus were within the fossiliferous Upper Cenomanian interval found to have first downhole occurrences within this immediately below the Plenus Marl Formation Crezone Cretarhabdus striatus and Lithraphidites acutum were tarhabdus striatus was only very rarely recorded in the only rarely recorded in the study area and the last present study and therefore was not used as a downhole occurrence of Zygodiscus minimus was not marker form This zone has not been assigned a prerecognised Reinhardtites fenestratus was noted to have fix NK or a number since its presence and thickness its first downhole occurrence within this zone is solely governed by the thickness of a lithological unit It is easily recognised from the "vipers tongue" 7.2.4.2 Parhabdolithus asper like response on the gamma logs, and characteristiPartial Range Zone NK 17 cally separates the Hod from Hidra Chalk Formations Even though it does not contain any age diagnostic A u t h o r : MORTIMER (this work) Probably equates with nannofossils, the Plenus Marl Formation is assigned Zone 10 (part) of SISSINGH (1977) and PERCH-NIELSEN a late Cenomanian age by direct comparison with on(& PRINS, 1979a) and the Eiffellithus turriseiffelii zone shore sections and the occurrence of well (part), the Microrhabdulus decoratus (part) and Lithraphidites documented earliest Turonian age marker nannofosacutum (part) subzones of CRUX (1982) sils just above it D e f i n i t i o n : Interval from the first downhole occurrence of Parhabdolithus asper to the first downhole appearance of Cribrosphaera primitiva (below micron size) 7.2.4 Hidra Formation (Cenomanian age) A g e : Upper to Middle Cenomanian The Hidra Formation represents the lowest unit of the L i t h o s t r a t i g r a p h i c U n i t : Hidra Formation (upper Chalk Group and has no reservoir potential in the study part) area This formation can be subdivided into nannofloral zones The distribution of the stratigraphically First appearances ( t o p s ) : Parhabdolithus asper, most important and commonly recorded species in this Zygodiscus theta and Octocyclus reinhardtii Formation are shown in Figure L a s t o c c u r r e n c e ( b a s e ) : Lithastrinus moratus R e m a r k s : PERCH-NIELSEN (& PRINS, 1979a) recognised the first downhole occurrence of Gartnerago nanum 7.2.4.1 Axopodorhabdus albianus and Cruciellipsis chiastia (= Microstaurus chiastius of this Partial Range Zone NK16 study) towards the top of SISSINGH'S Zone 10 (which A u t h o r s : CEPEK & HAY (1969) emended MORTIMER would probably relate to horizons within the NK 17 (this paper, non ROTH 1978) Equates with Zone 10 zone of this study) CRUX (1982) and the present au(part) of SISSINGH (1977) and PERCH-NIELSEN (& thor recognise the occurrence of Gartnerago nanum toPRINS, 1979a), the Eiffellithus turriseiffelii zone (part) and wards the base of the Cenomanian and Cruciellipsis Microrhabdulus decoratus subzone (part) of CRUX (1982) chiastia was found to have its extinction in the NK 16 D e f i n i t i o n : Interval from the first downhole appearzone PERCH-NIELSEN (& PRINS, 1979a) also note the ance of Axopodorhabdus albianus to the first downhole ap- last downhole occurrence of Ahmuellerella octoradiata, pearance of Parhabdolithus asper Microrhabdulus decoratus, Lithraphidites acutum and Corollithion exiguum within SISSINGH'S Zone 10 The exact reA g e : Late Cenomanian British Isles This formation is recognised as corresponding to the Barren/Impoverished zone described below and illustrated in Fig 167 ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at SISSINGH CHRONO STRATIGRAPHY (1977, CALCAREOUS NANNOPLANKTON ZONAL PALAEOCENE TERTIARY ZONE Nephrolithus frequens MAASTRICHTIAN UPPER Arkhangelskiella 25 B cymbitormis A Reinhardtites levis 24 B schemes used by SISSINGH (1977, 1978), 23 Tranolithus phacelosus A PERCH-NIELSEN (& PRINS, 1979a), CRUX (1982) and this work B 22 A Quadrum trifidum UPPER C Quadrum 21 B nitidum CAMPANIAN A Ceratolithoides aculeus 20 B 19 A LOWER B 18 Phanulithus ovalis Broinsonia parca [ s 1) A SANTONIAN UPPER CRETACEOUS UPPER LOWER 17 Phanulithus obscurus 16 Lucianorhabdus cayeuxii 15 Reinhardtites anthophorus Micula NP EXAMINED D1; k^ LAST NEPHROLITHUS FREQUENS Y k FIRST NEPHROLITHUS FREQUENS Y kt FIRST LITHRAPHIDITES QUADRATUS Y k FIRST ARKHANQELSKIELLA CYMBIFORMIS 26 Y L LAST TRANOLITHUS PHACELOSUS W L LAST ASPIDOLITHUS PAROUS ^ k LAST REINHARDTITES ANTHOPHORUS W L FIRST REINHARDTITES LEVIS staurophorä NANNOPLANKTON ZONAL ^ r INDICATORS FlftST CRUCIPLACOLITHUS TENUIS FIRST BIANTHOUTHUS k SPARSUS W k LAST NEPHROLITHUS FREQUENS V k FIRST NEPHROLITHUS FREQUENS Y~ FIRST LITHRAPHIDITES k QUADRATUS 25 Y~ FIRST ARKHANGELSKIELLA k CYMBIFORMIS ^ • L A S T REINHARDTITES k LEVIS Y~ LAST REINHARDTITES k LEVIS 24 Y' k LAST TRANOLITHUS PHACELOSUS W ' LAST ASPIDOLITHUS PARCUS Y k LAST REINHARDTITES ANTHOPHORUS V k FIRST REINHARDTITES LEVIS W FIRST QUADRUM L ' TRIFIDUM V ^ FIRST QUADRUM TRIFIDUM W L LAST CERATOLITHOIDES ARCUATUS Y' L LAST CERATOLITHOIDES ARCUATUS W k FIRST CERATOLITHOIDES ARCUATUS ^ k FIRST QUADRUM NITIDUM W L FIRST CERATOLITHOIDES ACULEUS W L LAST BUKRYASTER HAYI W L LAST MARTHASTERITES FURCATUS W L FIRST BUKRYASTER HAYI W L FIRST BROINSONIA PARCA CS 1) W ^ FIRST PHANULITHUS OBSCURUS r' ^ FIRST LUCIANORHABDUS CAYEUXII [ FIRST REINHARDTITES ^ ANTHOPHORUS 23 22 21 Y k 20 19 18 FIRST CERATOLITHOIDES AFICUATUS ^ k FIRST QUADRUM NITIDUM Y" k FIRST W L LAST BUKRYASTER HAYI Y' k LAST MARTHASTERITES FURCATUS W L FIRST BUKRYASTER HAYI W FIRST ASPIDOLITHUS L 16 CERATOLITHOIDES ACULEUS SP W FIRST PHANULITHUS W L FIRST LUCIANORHABDUS CAYEUXII J k FIRST REINHARDTITES ANTHOPHORUS 15 14 UPPER CONIACIAN CALCAREOUS ZONES AFTER , SISSINGH , 119 77 i A MARTINI 11971) + C LOWER Correction: In the last column (zonal indicators) Biscutum ellipticum must read Biscutum constms INDICATORS PERCH-NIELSEN AND PRINS ( a ) / PERCH - NIELSEN (1979b) D2 NOT LOWER 26 Fig 8: Comparison of the Upper Cretaceous 1S78) 14 ( s 1) ¥ FIRST MICULA " FIRST MICULA k STAUROPHORA (s 1) k DECUSSATA f FIRST MARTHASTERITES L FURCATUS Marthasterites LOWER 13 13 furcatus J FIRST MARTHASTERITES \ FURCATUS TURONIAN Lucianorhabdus UPPER 12 MODLE CENOMANIAN 168 W FIRST LUCIANORHABDUS " k MALEFORMIS k FIRST EIFFELLITHUS EXIMUS Quadrum 11 LOWER Ü| 12 maleformis 11 gartneri f L UPPER FIRST QUADRUM F GARTNERI ^ FIRST QUADRUM GARTNERI Microrhabdulus 10 10 decoratus MODLE f L LOWER UPPER FIRST MICRORHABDULUS " DECORATUS ^ FIRST MICRORHABDULUS DECORATUS Eillellithus turriseiffeli W f FIRST EIFFELLITHUS TURRISEIFFELI W " FIRST EFFELUTHUS TURRISEFFELI ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at CRUX (1982) CALCAREOUS THIS NANNOPLANKTON CALCAREOUS WORK NANNOPLANKTON 8UBZONE ZONAL ZONAL INDICATORS NP /* \ Arkhangelskieea cymbilormis NK1 INDICATORS Cruciplacolithus tenius (form with l e e t ) Thoracosphaera operculata • / • \\ Arkhangelskiella cymbilormis • Nephrolithus Irequens *t / Nephrolithus Irequens NK2 Zygodiscus spiralis MK3 NOT EXAMINED Gartnerago obliquum Gartnerago obliquum NK4 '• Phanulithus obscurus Phanulithus obscurus NK5 Reinhardtites levis Reinhardtites levis NK Tranolithus orionatus Tranolithus orionatus NK Broinsonia parca NKTT" J Broinsonia parca Orastrum campanensis Orastum campanensis NK9 -jHelicolilhus trabecutatus (above p size] Helicolithus t r a b e c u l a r s NK10 Prediscospiiaera stoveri Cylindralithus asymmetricus • Prediscosphaera stoveri Cylindralithus a s y m m e t r i c u s NK11 Broinsonia parca I Broinsonia • Broinsonia pa re a Crlbosphaera ehrenbergi 12A Broinsonia enormis NK12 _l Phanulithus Lucianorhabdus cayeuxii Lucianorhabdus cayeuxu Lucianorhabdus J Reinhardtiles anthophorus Reinhardtites anlhophorus obscurus 12B Lucianorhabdus cayeuxii ' Watznaueria b a r n e s a e e / i cayeux Ahmuellerelia octoradiata Lucianorhabdus malelormis g Lithastrinus mora tus Watznaueria barnesae NK13 ' enormis Micula staurophora 13A Watznaueria barnesae*/* Eitfellithus eximius B / « ~1 H e l i c o l i t h u s v a l h a l l e n s i s 13B 13C i_l M i c u l a Lucianorhabdus maleformis Micula staurophora Prediscosphaera cretecea staurophora 13D I Micula staurophora Eitfelithus Kamptnerius magnHicus 14B eximius Eitfellithus Ouadrum subsp gartneri Lucianorhabdus quadrilidus CyMndratu« coronatus Lithraphidites eximius Ouadrum gartneri -*-1 sub sp Microrhabdulus decoratus acutum _j Lithraphidites Prediscosphaera spinosa NOT HeScotithus valhallensis NK14 acutum «.J Kamptnerius magnificus EiffeMthus exfmfus 14C Lucianorhabdus « ! quadrifidus Microrhabdulus decoratus Eitfellithus turriseiffeli i Helicolithus valhallensis • / • Marthasterites turcatus »Martnasterltes turcatus 14A EHtellitrius eximius Quadrurrt gartnerit Lithastrinus sp • / • fc _&HPdEMra M!*Pt!l 142 Lithastrinus ftoraNs NK15 jpM%a^ABft|N/IMfovtRISHED AxopodomaDaus alblanus NK16 ZONEi?Zi00fl3% ~i A x o p o d o r h a b d u s ^ Parhabdolithus albianus asper ~» Cribrosphaera primitiva (below /i size) Crlbrosphaera primitiva I NK18 Gartnerago terago nanum ' K19 H Gartnerago nanum } C r i b r o s p h a e r a primitivaaft Biscutum eilipticum • / * Tetrapodornatodus EXAMINED First downhole occurrence Abundant Last downhole occurrence Common E x a c t r e l a t i o n s h i p b e t w e e n z o n a l b o u n d a r i e s used in this and the zones used by Slssingti (1977, 1978) are uncertain Synchronous nannotossil events D subzones alter Perch - N i e l s e n , study 1979b 169 ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at (& PRINS, 1979a) the Eiffellithus turriseiffelii zone (part), lationship of these events with respect to the NK 17 Prediscosphaera spinosa (part) subzone of CRUX (1982) zone of this paper is uncertain, since Corollithion exiguum was absent from this study, Lithraphidites acutumD e f i n i t i o n : Interval between the first downhole ocwas only rarely recorded and Ahmuellerella octoradiata currence of Gartnerago nanum to the first downhole ocwas found not to range below the Turonian CRUX currence of common/abundant Cribrosphaera primitva (1982) showed the first downhole occurrence of and/or Biscutum constans Parhabdolithus angustus and last downhole occurrencesA g e : Early Cenomanian of Cylindralithus coronatus and Microrhabdulus decoratus L i t h o s t r a t i g r a p h i c U n i t : Hidra Formation (lower within the Late Cenomanian, which would equate with part) the interval covering the NK 16 and NK 17 (part) F i zones of this paper Cylindralithus coronatus was not re- r s t a p p e a r a n c e s ( t o p s ) : Gartnerago nanum, Hemipodorhabdus gorkae, Nannoconus truitti corded in this study (perhaps because it is very prone to dissolution) Microrhabdus decoratus was found to haveL a s t o c c u r r e n c e s ( b a s e s ) : Gartnerago obliquum and its last downhole occurrence in the NK 18 zone and Zygodiscus theta Parhabdolithus angustus appeared to have a first dowR e m a r k s : The first downhole occurrence of Gartnerago nhole appearance higher in the Upper Cretaceous nanum is taken to approximate with the middle/early Cenomanian boundary for the purpose of this paper This form is shown by CRUX (1982) to have its first 7.2.4.3 Cribrosphaera primitiva downhole occurrence close to the middle/early Partial Range Zone NK18 Cenomanian boundary This generalisation has been A u t h o r : MORTIMER (this work) Equates with Zones 10 made because it is a form that is consistently re(part) and (part) of SISSINGH (1977) and PERCHcorded in the study area PERCH-NIELSEN (& PRINS, NIELSEN (& PRINS, 1979a); the Eiffellithus turriseilellii 1979a) noted the last downhole occurrence of Corolzone (part) and the Lithraphidites acutum subzone (part) lithion completum and the first downhole occurrence of of CRUX (1982) Braarudosphaera africana and Ellipsagelosphaera keftalrempti D e f i n i t i o n : Interval from the first downhole appearwithin the early Cenomanian None of these events ance of Cribrosphaera primitiva (below micron size) to were recognised in the present study CRUX (1982) inthe first downhole appearance of Gartnerago nanum dicated the last downhole occurrence of Corollithion kennedyi, Gartnerago obliquum, Pervilithus varius and LithA g e : Middle Cenomanian raphidites acutum, and the first downhole occurrence of L i t h o s t r a t i g r a p h i c U n i t : Hidra Formation (part) Ellipsagelosphaera forbesii, Parhabdolithus infinitus and F i r s t a p p e a r a n c e s ( t o p s ) : Cribrosphaera primitiva Zygodiscus erectus within the early Cenomanian Only (below micron size) and Ellipsagellosphaera ovata the last downhole occurrence of Gartnerago obliquum and Last occurrence ( b a s e ) : Microrhabdulus decoratus first downhole appearance of Parhabdolithus infinitus were noted to occur within the early Cenomanian in R e m a r k s : CRUX (1982) showed Zone 10 of SISSINGH this study, the other species being absent or very (1977) and PERCH-NIELSEN (& PRINS, 1979a) to range well within his Lithraphidites acutum subzone of middle rare Cenomanian age (which equates in part with the NK 18 zone of this paper) CRUX also noted the first 7.2.5 Upper / Lower Cretaceous Boundary, downhole occurrences of Corollithion kennedyi, LithraphiCenomanian / Albian dites pseudoquadratus and Lithraphidites alatus together with the last downhole occurrence of Cylindralithus biarcus in and Hidra Formation / Rodby Formation Boundaries the middle Cenomanian None of these events were Detailed descriptions and defining zones for the recognised in the present study CRUX (op cit.) also Lower Cretaceous is beyond the scope of the present listed the first downhole occurrence of Gartnerago nanum study Most wells drilled in the chalk hydrocarbon fields and Parhabdolithus asper within the middle Cenomanian terminate (T D.) within the Hidra Formation or topmost Both of these events were recognised in the present Cromer Knoll Group The uppermost Albian calcareous study but were found to have lower and higher ocnannofossils noted from the study area will, however, currences respectively compared to these findings be considered The distribution of the stratigraphically Only rare occurrences of Lithraphidites acutum and Litmost important and commonly occurring calcareous hraphidites alatus were recorded in this zone PERCHnannofossils is shown diagrammatically in Figure NIELSEN (& PRINS, 1979a) noted the last downhole ocD i s c u s s i o n : PERCH-NIELSEN (1979a) noted problems currences of Microrhabdulus decoratus, Lithraphidites acutum in recognising the Albian/Cenomanian boundary due and Corollithion exiguum at the base of zone 10 which to the correlation of coccolith stratigraphy with the probably equates to some point within NK 18 Zone stratotypes, but indicated the first downhole occurThe last downhole occurrence of Microrhabdulus derences of Hayesites albiensis, Braarudosphaera quinquecostata, coratus noted by SISSINGH (1977), which he equates to Braarudosphaera regularis and Braarudosphaera stenorhetha to the late/early Cenomanian boundary, also probably occur near to this horizon However, none of these occurs within this zone: The exact relationship of species were recorded in the present study THIERthese events to zone NK 18 of the present study is STEIN (1976) indicated that the last downhole occuruncertain rence of Lithraphidites alatus, which was only rarely found in this study, marked the Cenomanian/Albian 7.2.4.4 Gartnerago nanum boundary, but VERBEEK (1977) has recorded this Partial Range Zone NK19 species below the last downhole occurrence of Eiffellithus turriseiffelii (Late Albian) CRUX (1982) did not A u t h o r : MORTIMER (this work) Equates with the examine Albian age deposits but indicated, the EiffelZone (part) of SISSINGH (1977) and PERCH-NIELSEN 170 ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at this method in nannofossil biostratigraphy has only recently been undertaken and in this study has proved to be very useful It is hoped that this method will be more extensively used in industry, although with the limitation that these acmes or influxes may be influenced by environmental constraints (and may, therefore, be diachronous on a regional scale, although on a local (Block) or field scale they may be extremely useful) The two acme tops used in this study to define the tops of the lithus turriseiffelii zone ranging into the upper Albian, based on the studies of THIERSTEIN (1971), SISSINGH (1977) and MANIVIT et al (1977) Similarly, TAYLOR (1982) recognised the base of the Eiffellithus turriseiffelii zone within the upper Albian, but was unable to define the upper limit of this boundary since the study of Cenomanian age deposits was beyond the scope of her study In the present study the Upper/Lower Cretaceous boundary, which coincides with the Hidra/Rodby ForWatznaueria barnesae N K and Helicolithus valhallensis mation boundary, is marked by an abundant first NK14 Zones, have been recognised throughout downhole occurrence of Biscutum constans and/or Cribromost of the North Sea Basin sphaera primitiva These events are almost certainly related in some way to the lilthological change from © Some species have been found to have reduced chalky limestones of the Hidra Formation to the argilstratigraphic ranges compared to those previously laceous limestones and calcareous claystones of the reported, due probably to preservation or environRodby Formation of Late Albian age It is interesting mental factors They may, however, be used on a to note that the foraminiferal assemblages recorded local basis at this boundary are dominated by hedbergellids, a Q In certain parts of the scheme, the events are apgroup whose distribution pattern is linked to the proproximated to the stage boundaries, particularly ximity to the shoreline If their presence is governed where there is no direct comparison with other disby lithology then this event will be diachronous, alciplines though they have been recognised consistently in the study area and dated accurately by palynological Acknowledgements means The recognition of these two events is depenThe author is indebted to the Directors of Robertson Redent on sampling and thickness of the Upper Albian search International for allowing permission to publish the data section, which can be quite condensed in the study used in this paper Thanks go to John CHURCH, Keren OWERS and Nick MILES (Robertson Research International) for their area The subsequent first downhole appearances of Tetrapodorhabdus coptensis and Grantarhabdus meddii appear to be the next biostratigraphically important nannofossil events in the Upper Albian of the study area critical suggestions and comments and Dr Victor H HITCHINQS (Shell The Hague) and Dr Katharina PERCH-NIELSEN for critical reading of the manuscript The help of Alice LEOW (drafting) and Agnes KWOK (typing) of Robertson Research Singapore is much appreciated without whose help this paper could not have been completed Conclusions O The scheme presented in the preceeding sections was designed for use in the oil industry Q The main basis for the scheme is the use of stratigraphic (first downhole occurrences) and acme tops of species for zonal subdivision of the Upper Cretaceous Stratigraphic bases of species (last downhole occurrences) are used for subzonal markers and are of secondary importance Q The scheme has been found to work in the study area and hopefully will be developed and modified further to include other areas of the North Sea Basin when more well material is released O Difficulty has arisen in correlating this scheme with other disciplines particularly macrofossils In the case of foraminifera direct correlation is hampered by the poor preservation, and lack of many age diagnostic planktonic forms Palynology is not routinely carried out in chalk sections because the nature of the lithology is not conducive to good palynomorph recovery Preliminary studies in the Northern North Sea in the more argillaceous Shetland Group indicate that greater integration between the three disciplines will probably be achieved The use of species acme tops over the Santonian to Turonian interval proved the only reliable method to subdivide this section on the basis of calcareous nannofossils Palynology has often used acmes and influxes of various species to subdivide certain parts of the Mesozoic and Cenozoic The application of Appendix Taxonomy This appendix lists the 56 most important calcareous nannofossils recorded in this study, in downhole stratigraphic order Reference is made to the original description together with any subsequent emendments Brief remarks are made where applicable O Thoracosphaera operculata BRAMLETTE & MARTINI 1964 BRAM- LETTE and MARTINI 1964 p 305; pi 5, figs - O Markalius inversus (DEFLANDRE, in DEFLANDRE & FERT 1954) BRAMLETTE & MARTINI 1964 DEFLANDRE (1954) p 150; & MARTINI (1964) p 302; pi 2, figs - ; pi 7, figs a - b O Neocrepidolittius dirimosus (PERCH-NIELSEN 1979b) pi 9, figs - PERCH- NIELSEN 1981 (not figs - ) PERCH-NIELSEN BRAMLETTE (1979b) p 124; pi 2, figs - , 23, 24 PERCH-NIELSEN (1981) fig plate O Neocrepidolittius neocrassus (PERCH-NIELSEN 1968) ROMEIN 1979 PERCH-NIELSEN (1968) p 36; pi 2, fig 9, text-fig 11 ROMEIN (1979) p 183; pi 1, fig O Neocrepldolithus NIELSEN 1981 cruclatus (PERCH-NIELSEN 1979b) PERCH- PERCH-NIELSEN p 124; pi 2, (1979b) figs 1 - , 25, 26 R e m a r k s : ROMEIN (1979) introduced the genus Neocrepidolittius to distinguish it from the Jurassic genus Crepidolithus NOEL 1968 by the imbrication of the elements in the wall O Arkhangelskiella cymbiformis VEKSHINA 1959 VEKSHINA (1959) p 66; pi 2, figs a - R e m a r k s : Arkhangelskiella cymbiformis is used in this study to include all normally perforate species which some authors would assign to Arkhangelskiella specillata VEKSHINA 1959 because they cannot be distinguished from one another due to preservational constraints in particular overgrowth cementation 171 ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at O Lucianorhabdus cayeuxii DEFLANDRE 1959 DEFLANDRE (1959) O p 142; pi 4, figs 11-25 R e m a r k s : Lucianorhabdus cayeuxii was the only species of Lucianorhabdus to be consistently recognised in the study O area O Micula staurophora (GARDET 1955) STRADNER 1963 GARDET O Cribrosphaera ehrenbergii ARKHANGELSKY 1912 ARKHANGELSKY (1912) p 142; pi 6, figs 19, 20 GARTNER (1968) p 40; pi 1, figs 14, 15; pi 3, fig 2; pi 6, fig 7; pi 12, fig 2; O pi 15, fig 11 R e m a r k s : There appears to be extensive variation in outline shape of Cribrosphaera ehrenbergii ranging from elliptical toO circular in the forms recorded in this study However, shape is not considered to be a viable criterion to subdivide this species Since only light microscope studies were carried out, the species Cribrosphaera ehrenbergii inO cludes all these variously shaped forms text-fig 65, pi 8, figs 15-16 REINHARDT (1965) p 32 R e m a r k s : PERCH-NIELSEN (1979a) fig 12 illustrated several species which appear to be very similar to Eiffellithus turriseiffelii but are distinguished from one another on differences in structure In most cases, particularly when the spine is missing, it is very difficult to subdivide them They are for the purpose of this study all included in Eiffellithus turriseiffelii except where distinct differences can be identified Dodekapodorhabdus noeliae PERCH-NIELSEN 1968 PERCH- NIELSEN (1968) p 47; pi 8, figs - ; pi 9, fig - MARTINI (1964) p 303; pi 14, figs - p 318; pi 6, figs - 1 O R e m a r k s : Micula staurophora is used in preference to Micula decussata VEKSHINA 1959 in this study O Kamptnerius magnificus DEFLANDRE 1959 DEFLANDRE (1959) O p 135; pi 1, figs - R e m a r k s : See THIERSTEIN (1976) for list of synonyms of this species (THIERSTEIN [op cit.] included Kamptnerius punctatus STRADNER 1963 in this list) This form has been O recognised in the Northern North Sea in well preserved material generally in the absence of K magnificus In the study area no perforate forms were recorded due to preservational constraints and because of this K magnificus is O taken to include all these normally perforate forms O Eiffellithus turriseiffelii (DEFLANDRE in DEFLANDRE and FERT 1954) REINHARDT 1965 DEFLANDRE & FERT (1954) p 149; pi 22, figs 3, O Zygodiscus spiralis BRAMLETTE & MARTINI 1964 BRAMLETTE & (1955) p 534; pi 10, fig 96 BRAMLETTE & MARTINI (1964) O Ahmuellerella octoradiata (GORKA 1957) REINHARDT 1966 GORKA (1957) p 259; pi 4, fig 10 REINHARDT (1966) p 24; Gartnerago obliquum (STRADNER 1963) THIERSTEIN 1974 STRADNER (1963) p 10; pi 1, fig THIERSTEIN (1974) p 640; pi 5, fig - ; pi 6, figs - ; pi 7, figs - Prediscosphaera stoveri (PERCH-NIELSEN 1968) WIND & WISE 1976 PERCH-NIELSEN (1968) p 66; pi 6, figs 11-13 WIND & WISE (1976) p 305; pi 42, fig Phanulithus obscurus (DEFLANDRE, 1959) WIND & WISE 1976 DEFLANDRE (1959) p 138; pi 3, figs - WIND & WISE (1976) p 304; pi 31, fig 5; pi 33, figs - ; pi 34, figs 2, 4; PI 36, fig Reinhardtites levis PRINS & SISSINGH 1977 PRINS & SISSINGH (1977) p 61; pi 1, figs - Tranolithus orionatus (REINHARDT 1966a) REINHARDT 1966b REINHARDT (1966a) p 42; pi 23, figs 22, - 3 REINHARDT (1966b) p 522 Broinsonia parca (STRADNER 1963) BUKRY 1969 STRADNER (1963) p 10; pi 1, figs 3, 3a BUKRY (1969) p 23; pi 3, figs - Reinhardtites anthophorus (DEFLANDRE 1968, SISSINGH 1977 DEFLANDRE 1959) PERCH-NIELSEN (1959) p 137; pi 1, figs 21, 22 PERCH-NIELSEN (1968) (pars) p 38; pi 5, figs 1, 5, (non text-figs 13, 14, pi 5, figs - , 7, 8) SISSINGH (1977) p 61; pi 1, figs a - d Orastrum campanensis (CEPEK 1970) WIND & WISE 1976 CEPEK (1970) p 246-247; pi 25, figs 1, O Helicolithus trabeculatus (GORKA 1957) VERBEEK 1977 GORKA (1957) p 277; pi 3, fig REINHARDT & GORKA (1967) p 250; pi 31, figs 19, 23; pi 32, fig 1; text fig O Quadrum gartneri PRINS & PERCH-NIELSEN 1977 PRINS & PERCH-NIELSEN (1977) p 177; pi 1, figs - O Eiffellithus eximius (STOVER 1966) PERCH-NIELSEN 1968 STOVER (1966) p 138; pi 2, fig 15, 16; pi 8, fig 15 PERCH-NIELSEN (1968) p 30; pi 3, figs - O Prediscosphaera cretacea (ARKHANGELSKY 1912) GARTNER 1968.O Cylindralithus asymmetricus BUKRY 1969 BUKRY (1969) p 42; pi 19, figs - ARKHANGELSKY (1912) p 410; pi 6, figs 12, 13 GARTNER O (1968) p 19; pi 2, figs - ; pi 3, fig 8; pi 4, figs 19-24; pi 6, figs 14, 15; pi 9, figs - ; pi 12, figs 1; pi 14, figs - 2 ; pi 18, fig 8; pi 22, figs - ; O pi 23, figs - ; pi 25, figs 12-14; pi 26, fig Remarks: The various subspecies of Prediscosphaera cretacea O have all been grouped together since they are not preserved (well enough) to be able to recognise the subtle difO ferences used to differentiate them under the light microscope O Watznaueria barnesae (BLACK (1968) p 33; pi 1, fig MANIVIT (1971) p 105-106; pi 1, figs - Lithastrinus floralis STRADNER 1962 STRADNER (1962) p 370-372; pi 2, figs - 1 Lithastrinus moratus STOVER 1966 STOVER (1966) p 149; pi 7, fig 20 Marthasterites furcatus (DEFLANDRE in DEFLANDRE & FERT 1954) DEFLANDRE 1959 DEFLANDRE & FERT (1954) p 168; pi 13, fig 14 DEFLANDRE (1959) p 139; pi 2, figs - ; pi 3, figs 1, O Helicolithus valhallensis MORTIMER new species (MORTIMER in prep.) R e m a r k s : A species of Helicolithus in which the cross bars are subaxially aligned 1959) PERCH-NIELSEN 1968 BLACK (1959) p 325; pi 9, figs 1, PERCH-NIELSEN (1968) p 69; fig 32, pi 22, figs - ; pi 23, figs 1, 4, 5, 16 O Ahmuellerella regularis (GORKA Broinsonia enormis (SHUMENKO 1968) MANIVIT 1971 SHUMENKO 1957) BUKRY 1969 VERBEEK 1977 GORKA (1957) p 246; pi 2, fig GARTNER (1968) O Biscutum constans (GORKA 1957) BLACK in BLACK & BARNES p 23; pi 3, fig 12; ph 5, figs - ; pi 6, figs - ; 1959 GORKA (1957) p 279; pi 4, fig BLACK & BARNES pi 12, fig 11 (1959) p 325; pi 10, fig O Prediscosphaera grandis PERCH-NIELSEN (1979a) PERCHO Parhabdolithus achlyostaurion HILL (1976) HILL (1976) NIELSEN (1968) (1979a) BRAMLETTE & MARTINI (1964) p 30; p 145-146; pi 9, figs - pi 2, figs 13-16 PERCH-NIELSEN (1968) pi 13, figs 1, 5, 6; pi 14, fig PERCH-NIELSEN (1979a) p 267; pi 2, fig O Nephrolithus frequens (GORKA 1957) REINHARDT & GORKA 1967 GORKA (1957) p 282; pi 5, fig REINHARDT & GORKA (1967) pi 32, figs - O O Axopodorhabdus albianus (BLACK 1965) BLACK 1967, WIND & WISE 1976 BLACK (1965) p 133; fig 10 BLACK (1967) p 143-144 WIND & WISE (1976) p 297 O Microstaurus chiastius (WORSLEY 1971) GRÜN in GRÜN & AL- LEMANN 1975 WORSLEY (1971) pi 310; pi 1, figs - 4 Lithraphidites quadratus BRAMLETTE & MARTINI 1964 BRAMLETTE & MARTINI (1964) p 310; p 106, figs 16, 17; pi 7, fig GRÜN in GRÜN & ALLEMANN (1975) p 181; text-fig 22; pi V, O Prediscosphaera arkhangelsky! (REINHARDT 1965) PERCH-NIELSEN 1984 REINHARDT (1965) p - ; pis - , text-figs - PERCH-NIELSEN (1984) p 43 O figs - Reinhardtites fenestratus (WORSLEY 1971) THIERSTEIN in ROTH & THIERSTEIN 1972 WORSLEY (1971) p 1305; pi 1, figs 3 - ROTH & THIERSTEIN (1972) p 437; pi 8, O Microrhabdulus decoratus DEFLANDRE 1959 DEFLANDRE (1959) figs - p 140; pi 4, figs - 1963) MANIVIT 1971 O Prediscosphaera honjoi BUKRY 1969 BUKRY (1969) p 39; O Parhabdolithus asper (STRADNER STRADNER (1963) p 177; pi 2, figs - MANIVIT (1971) pi 18, figs - O Grantarhabdus coronadventis (REINHARDT 1966a) GRÜN in GRÜN p 87; pi 23, figs - O Cribrosphaera primitiva THIERSTEIN 1974 THIERSTEIN (1974) & ALLEMANN 1975 REINHARDT (1966a) p 26; pi 23, fig 29, p 637; pi 1, figs - 30 GRÜN in GRÜN & ALLEMANN (1975) p 184 172 ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at O CRUX, J A.: A biostratigraphical study of Upper Cretaceous calcareous nannofossils from south-east England and north France - University of London, unpublished thesis, 1-299, Zygodiscus theta (BLACK in BLACK & BARNES 1959) BUKRY 1980 1969 BLACK & BARNES (1959) p 327; pi 12, fig BUKRY CRUX, J A.: New calcareous nannofossil taxa from the Cre(1969) p 62; pi 36, figs 7, taceous of South East England - Neues Jahrbuch für Ellipsagelosphaera ovata (BUKRY 1969) BLACK 1973 BUKRY Geologie und Paläontologie, Monatshefte 1981, 633-640, (1969) (partim) p 33; pi 11, fig 11 (non fig 12) BLACK 1981 (1973) p ; pi 26, figs 10-12 CRUX, J A.: Upper Cretaceous (Cenomanian to Campanian) Gartnerago nanum THIERSTEIN, 1974 THIERSTEIN (1974) p 637; calcareous nannofossils In LORD, A R (Ed.): A Stratigpi 2, figs 1-13 raphical Index of Calcareous Nannofossils - Brit MicropaNannoconus truitti BRÖNNIMANN 1955 BRÖNNIMANN (1955) laeontol Soc Ser., - , 1982 p 38; pi 2, figs - , 7; text-figs f - j Hemipodorhabdus gorkae (REINHARDT 1969) GRÜN in GRÜN &DEEGAN, C E & SCULL, B J (compilers): A proposed standard lithostratigraphic nomenclature for the Central and Northern ALLEMANN 1975 REINHARDT (1969) p 933; pi 1, figs - GRÜN & ALLEMANN (1975) p 171-172 North Sea - Inst Geol Sei., No 77/25; Bull Norw Pet DiTetrapodorhabdus coptensis BLACK 1971 BLACK (1971) p 411; rect., No 1, 33 pp., 1977 pi 31, fig DEFLANDRE, G.: Sur les nannofossiles calcaires et leur sysGrantarhabdus meddii BLACK 1971 BLACK (1971) p 403; pi 33, tematique - Revue de Micropaleontologie, 2, 127-152, fig 1959 Octocyclus reinhardtii (BUKRY 1969) W I N D & WISE 1976 BUKRY (1969) p 38; pi 16, fig WIND & WISE (1976) p 302; pi 57, fig 6; pi 58, figs 1, O O O O O O O DEFLANDRE, G References AFEJUKU, A.: Albian to Cenomanian calcareous nannoplankton from N W Europe - University of London, unpublished thesis, 1-247, London 1980 ARKHANGLESKY, A D.: Upper Cretaceous deposits of East European Russia - Materialien zur Geologie Rußlands, 25, - , 1912 BLACK, M.: Coccoliths - Endeavour, 24, 131-137, 1965 BLACK, M.: New names for some coccolith taxa - Proceedings of the Geological Society of London, 1640, 139-145, 1967 BLACK, M.: Coccoliths of the Speeton Clay and Sutterby Marl - Proceedings of the Yorkshire Geological Society, 38, 381-424, 1971 BLACK, M.: British Lower Cretaceous Coccoliths Gault Clay Palaeontographical Society Monograph, 126, - (Pt 1); 127, - 1 (Pt 2); 129, 113-142 (Pt 3)., 1972, 1973, 1975 BLACK, M.& BARNES, B.: The structure of coccoliths from the English Chalk - Geological Magazine, 96, 321-328, 1959 BRAMLETTE, M N & MARTINI, E.: The great change in Calcareous Nannoplankton between the Maastrichtian and the Danian - Micropaleontology, 10, 291-322, 1964 BRÖNNIMANN, P.: Microfossils incertae sedis from the Upper Jurassic and Lower Cretaceous of Cuba - Micropaleontology, 1, - , 1955 BREWSTER, J & DANGERFIELD, J A.: Chalk fields along the Lindesnes Ridge, Eldfisk - Mar Pet Geol., V o l , No 3, 239-278, 1984 BUKRY, D.: Upper Cretaceous coccoliths from Texas and Europe - University of Kansas Paleontological Contributions, Article 51 (Protista 2), - , 1969 BUKRY, D.: Low-latitude coccolith biostratigraphic zonation Initial Reports of the Deep Sea Drilling Project, XV, 685-703, 1973 BUKRY, D.: Cretaceous and Paleogene coccolith stratigraphy, Deep Sea Drilling Project, Leg 26 - Initial Reports of the Deep Sea Drilling Project, XXVI, 669-673, 1974 BUKRY, D.: Coccolith and silicoflagellate stratigraphy, northwestern Pacific Ocean, Deep Sea Drilling Project Leg 32 Initial Reports of the Deep Sea Drilling Project, XXXII, 7 - , 1975 BUKRY, D & BRAMLETTE, M N.: Coccolith age determinations Leg 3, Deep Sea Drilling Project - Initial Reports of the Deep Sea Drilling Project, III, - 1 , 1970 CEPEK, P.: Zur Vertikalverbreitung von Coccolithen-Arten in der Oberkreide NW-Deutschlands - Geol Jb., v 88, 235-264, 1970 CEPEK, P & HAY, W W.: Calcareous nannoplankton and biostratigraphic subdivisions of the Upper Cretaceous - Transactions of the Gulf Coast Association of Geological Societies, 19, 323-336, 1969 & FERT, C: Observations sur les coc- colithophorides actuels et fossiles en microscopie ordinaire et electronique - Annales Paleontologie, 40, 115-176, 1954 D'HEUR, M.: Chalk Reservoir of the West Ekofisk Field In: the Sedimentation of the North Sea Reservoir Rocks, Geilo, 1 - , May 1980 - Norw Pet S o c , 20 pp., 1980 D'HEUR, M.: Porosity and hydrocarbon distribution on the North Sea chalk reservoirs - Mar Pet Geol., vol 1, No 3, 211-238, 1984 FORCHHEIMER, S.: Scanning electron microscope studies of Cretaceous coccoliths from Köpingsberg Borehole No 1, S E Sweden - Sveriges Geologiska Undersökning C668, Arsbok, 65/14, - , 1972 GARDET, M.: Contribution ä l'etude des coecolithes des terrains neogenes de l'Algerie - Publications du Service de la Carte G6ologique de l'Algerie, Serie 2, Bulletin 5, 477-550, 1955 GARTNER, S.: Coccoliths and related calcareous nannofossils from Upper Cretaceous deposits of Texas and Arkansas University of Kansas Paleontological Contributions, Article 48 (Protista 1), - , 1968 GORKA, H.: Les Coccolithophorides du Maestrichtien superieur de Pologne - Acta Palaeontologia Polonica, 2, 235-284, 1957 GRÜN, W & ALLEMANN, F.: The Lower Cretaceous of Caravaca (Spain); Berriasian calcareous nannoplankton of the Miravetes Section (Subbetic Zone, Prov of Murcia) - Eclogae Geologicae Helvetiae, 68, - 1 , 1975 HARDMAN, R F P & EYNON, G.: Valhall Field - A structural/ stratigraphic trap In FINSTAD, K G & SELLY, R G (eds.): Mesozoic Northern North Sea Symposium - Proc Norw Pet Soc Pap MNNSS/14, 33 pp., 1977 HARDMAN, R F P & KENNEDY, W J.: Chalk reservoirs of the Hod Field, Norway In: The Sedimentation of the North Sea Reservoirs Rocks, Geilo, 11.-14 May 1980 - Norw Pet Soc, 31 pp., 1980 HARDMAN, R F P.: Chalk reservoirs of the North Sea - Bull Geol Soc Denmark, Vol.30, 119-137, 1982 HATTNER, J G., WIND, F H & WISE, S W.: The Santonian - Campanian Boundary Comparison of Nearshore-Offshore Calcareous Nannofossils Assemblages - Cahiers de Micropaleontologie, 3, - , pis., 1980 HAY, W W.: Calcareous Nannofossils In RAMSAY, A T S (Ed.): Oceanic Micropalaeontology - 2, 1055-1200, London (Academic Press) 1977 HAY, W W & MOHLER, H P.: Calcareous nannoplankton from Early Tertiary rocks at Pont Labau, France, and Paleocene - Early Eocene correlations - Journal of Paleontology, , 1505-1541, 1967 HAY, W W & TOWE, K M.: Microrhabdulus belgicus, a new species of nannofossil: Micropalaeontology, v no 1, - , pi 1, 1963 HESJEDL, L A & HAMAR, G P.: Lower Cretaceous Stratigraphy and Tectonics of the South-Southeastern Norwegian Off- 173 ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at Kongelige Danske Videnskabernes Selskab, Biologiske Skrifter, 16, 1-96, 1968 PERCH-NIELSEN, K.: Remarks on Late Cretaceous to Pleistocene Coccoliths from the North Atlantic In LAUGHTON, A S., BERGGREN, W A et al - Init Repts D S D P., 12, 1003-1069, Washington (U S Govt Printing Office), 1972 PERCH-NIELSEN, K.: Neue Coccolithen aus dem Maastrichtien von Dänemark, Madagaskar und Ägypten - Geol Soc 103-179, 1976 Denmark Bull., v 22, 306-333, 1973 PERCH-NIELSEN, K.: Albian to Pleistocene calcareous nanILLING, L V & HOBSON, G D.: Petroleum Geology of the Continofossils from the Western South Atlantic, D S D P Leg nental Shelf of North-West Europe - Institute of Petroleum, 39 - Initial Reports of the Deep Sea Drilling Project, 1980 XXXIX, 699-823, 1977 PERCH-NIELSEN, K.: Calcareous Nannofossils from the CreKENNEDY, W J.: Aspects of Chalk Sedimentation in the taceous between the North Sea and the Mediterranean In: Southern Norwegian Offshore In: The Sedimentation of the Aspekte der Kreide Europas - I U G S Series A, 6, North Sea Reservoir Rocks, Geilo, 11 - May 1980 223-272, Stuttgart 1979a Norw Pet Soc, 1980 PERCH-NIELSEN, K.: Calcareous nannofossil zonation at the Cretaceous / Tertiary boundary in Denmark In BIRKELUND, T & BROMLEY, R G (Eds.) - Cretaceous - Tertiary BounLEZAUD, L.: Nannofossiles calcaires du Jurassique superieur dary Events, I, 115-135 (+ pages references), University de la Baie de Seine - Bulletin de la Societe Geologique de of Copenhagen, Copenhagen 1979b Normandie, 57, - , 1968 PERCH-NIELSEN, K.: New Maastrichtian and Paleocene calLYULEVA, S A.: Kokolitoforidi Turons'kikh vidkladiv Dniprov'sko careous nannofossils from Africa, Denmark, the U S A and - Donets'koy Zapadini (coccolihtophoridae in the Turonian the Atlantic, and some Paleocene lineages - Eclogae geol strata of the Dniepr - Don basins): Geol Zhur., v 27, no 6, Helv Vol 74/3, 831-863, 1981 - , pis 1-4, 1967 PERCH-NIELSEN, K: Mesozoic calcareous nannofossils - In: MANIVIT, H.: Les nannofossiles calcaires du Cretace frangais Plankton Stratigraphy - Cambridge Earth Science Series, (Aptien - Maestrichtien) Essai de biozonation appuyee sur Chapter 10, 329-426, 1985 les stratotypes - These, Universite de Paris, 1-187, Paris PFLAUMANN, U & CEPEK, P.: Cretaceous foraminiferal and nan1971 noplankton biostratigraphy and paleoecology along the West MANIVIT, H., PERCH-NIELSEN, K., PRINS, B & VERBEEK, J W.: African Continental Margin In VON RAD, U., HINZ, K., SARNMid Cretaceous calcareous nannofossil biostratigraphy THEIN, M & SEIBOLD, E (Eds.): Geology of the Northwest AfProceedings of the Koninklijke Nederlandse Akademie von rican Continental Margin - Berlin - Heidelberg - New Wetenschappen, B 80, - , 1977 York (Springer Verlag), 309-353, 1982 MARTINI, E.: Standard Tertiary and Quaternary calcareous PRINS, B.: Meeting on mid-Cretaceous nannofossils - Worknannoplankton zonation - Proceedings of the II Planktonic ing Papers (quoted in CRUX, 1982), The Hague 1977 Conference, Roma 1970, 2, 739-785, 1971 REINHARDT, P.: Einige Kalkflagellaten-Gattungen (CocMARTINI, E.: Cretaceous to Recent calcareous nannoplankton colithophoriden, Coccolithineen) aus dem Mesozoikum from the central Pacific Ocean (D S D P Leg 33) Initial Deutschlands - Monatsberichte der Deutschen Akademie Reports of the Deep Sea Drilling Project, XXXIII, 383-423, der Wissenschaften zu Berlin, 6, 749-759, Berlin 1964 1976 REINHARDT, P.: Neue Familien für fossile Kalkflagellaten (CocMARTINI, E & WORSLEY, T.: Standard Neogene calcareous colithophoriden, Coccolithineen) Monatsberichte der nannoplankton zonation - Nature, 225, 289-290, 1970 Deutschen Akademie der Wissenschaften zu Berlin, 7, MICHELSEN, O (Ed.): Geology of the Danish Central graben - , 1965 Danm geol unders., Ser 13/8, 1-33, 1982 REINHARDT, P.: Zur Taxonomie und Biostratigraphie des fossiMAPSTONE, N B.: Diagenetic history of a North Sea Chalk len Nannoplanktons aus dem Malm, der Kreide und dem Sedimentology 22, 601-613, 1975 Alttertiär Mitteleuropas Freiberger Forschungshefte, MORTIMER, C P.: Cenomanian to Lower Turonian Calcareous Paläontologie, C196, - , 1966a Nannoplankton from parts of Southern and Eastern England REINHARDT, P.: Fossile Vertreter coronoider und styloider - University of London, unpublished thesis, 1-153, 1981 Coccolithen (Familie Coccolithaceae POCHE 1913) MORTIMER, C P.: Helicolithus i/alhallensis a new Upper CretaceMonatsberichte der Deutschen Akademie der Wissenschafous calcareous nannofossil from the North Sea Chalk Hydten zu Berlin, 8, 513-524 rocarbon Province - In prep REINHARDT, P.: Fossile Coccolithen mit rhagoidem Zentralfeld MORTIMER, C P.: The distribution of calcareous nannofossils (Farn Ahmuellerellaceae Subord Coccolithineae) - Neues across the Turonian/Cenomanian boundary at Nettleton Jahrbuch für Geologie und Paläontologie, Monatshefte Quarry Lincolnshire - In Prep 1967, 163-178, 1967a MÜLLER, C.: Calcareous nannofossils from the North Atlantic REINHARDT, P.: Zur Taxonomie und Biostratigraphie der Coc(Leg 48) In: MONTADERT, L., ROBERTS, D G et al - Init colithineen (Coccolithophoriden) aus dem Eozän Repts D S D P., 48, 589-640, Washington (U S Govt Norddeutschlands - Freiberger Forschungshefte, PaläonPrinting Office) 1979 tologie, C213, - , 1967b REINHARDT, P & GORKA, H.: Revision of some upper CretaceNOEL, D.: Note preliminaire sur les coccolithes jurassiques ous coccoliths from Poland and Germany - Neues Cahiers de Micropaleontologie, 1, 1-12, 1965a Jahrbuch für Geologie Paläontologie, Abh., v 129, NOEL, D.: Sur les coccolithes du Jurassique europeen et d'Af240-255, 1967 rique du Nord Essai de Classification des coccolithes fossiles - Editions du Centre national de la Recherche ScienROBERTSON RESEARCH INTERNATIONAL LIMITED: Southtifique, Paris, 1-209, Paris 1965b ern Offshore Norway The Stratigraphy and Petroleum Geochemistry of the Jurassic to Tertiary Sediments, 1979 NOEL, D.: Coccolithes Cretaces La craie campanienne du Bassin de Paris - Editions centre national Recherche ROBERTSON RESEARCH INTERNATIONAL LIMITED: Southern Offshore Norway Phase Two Study: The Stratigraphy Scientifique, Paris, 129 p., 48 pls., 23 figs., Paris 1970 and Petroleum Geochemistry of the Jurassic to Tertiary SedOFSTAD, K.: Geology of the southernmost part of the Norwegiments, 1982 ian section of the Central Trough NDP Paper No 32, 1983 ROBERTSON RESEARCH INTERNATIONAL LIMITED: The PERCH-NIELSEN, K.: Der Feinbau und die Klassifikation der Danish North Sea Area: The Stratigraphy and Petroleum Coccolithen aus dem Maastrichtien von Dänemark - Det shore - In: Petroleum Geology of Southeastern North Sea and Adjacent Onshore Areas - The Hague, 1982, 1983 HEDBERG, H D (ed.): International stratigraphic guide A guide to stratigraphic classification, terminology, and procedure (John Wiley and Sons) 1976 HILL, M E.: Lower Cretaceous calcareous nannofossils from Texas and Oklahoma Palaeontographica B 156, 174 ©Geol Bundesanstalt, Wien; download unter www.geologie.ac.at Geochemistry of the Jurassic to Tertiary Sediments, 1983 ROMEIN, A J T.: Evolutionary lineages in Early Paleogene calcareous nannoplankton - Utrecht Micropaleontological Bulletin, 22, - , 1979 ROOD, A P., HAY, W W & BARNARD, T.: Electron Microscope Studies of Oxford Clay Coccoliths - Eclogae Geologicae Helvetiae, 64, 245-272, 1971 ROTH, P H : Calcareous nannofossils - Leg 17, Deep Sea Drilling Project, XVII, 695-795, 1973 ROTH, P H : Cretaceous Nannoplankton Biostratigraphy and Oceanography of the Northwestern Atlantic Ocean - Initial Reports of the Deep Sea Drilling Project, XLIV, 731-759, 1978 ROTH, P H & THIERSTEIN, H R.: Calcareous nannoplankton - Leg 14 of the Deep Sea Drilling Project - Initial Reports of the Deep Sea Drilling Project, XIV, 421-486, 1972 SHAFIK, S.: A new nannofossil zone based on the Santonian Gingin Chalk, Perth Basin, Western Australia - Bureau of Mineral Resources, Journal of Australian Geology and Geophysics, 3, 211-226, 1978 SHAFIK, S & STRADNER, H.: Nannofossils from the eastern desert, Egypt, with reference to Maastrichtian nannofossils from the U S S R - Jb Geol B.-A., 17, - , 50 pis., figs., Vienna 1971 SKOVBRO, B: Depositional conditions during Chalk sedimentation in the Ekofisk area Norwegian North Sea In: Petroleum Geology of Southeastern North Sea and Adjacent Onshore Areas, 169-175, The Hague 1983 SHUMENKO, S I.: Some aspects of the ontogenesis, variation and taxonomy of fossil coccolithophorids revealed by electron microscopic studies - Paleontol Zh., 4, - (in Russian), 1968 SISSINGH, W.: Biostratigraphy of Cretaceous calcareous nannoplankton - Geologie en Mijnbouw, 56, - , 1977 SISSINGH, W.: Microfossil biostratigraphy and stage-stratotypes of the Cretaceous - Geologie en Mijnbouw, 57/3, 433-440, 1978 SMITH, C C : Upper Cretaceous calcareous nannoplankton zonation and stage boundaries - Transactions of the Gulf Coast Association of Geological Societies, 25, 263-278, 1975b STOVER, L E.: Cretaceous coccoliths and associated nannofossils from France and the Netherlands - Micropaleontology, 12, 133-167, 1966 STRADNER, H.: Die fossilen Discoasteriden Österreichs II Teil - Erdöl-Zeitschrift, 75, 472-488, 1959 STRADNER, H.: Vorkommen von Nannofossilien im Mesozoikum und Alttertiär - Erdöl-Zeitschrift, 77, 7 - 8 , 1961 STRADNER, H.: Über neue und wenig bekannte Nannofossilien aus Kreide und Alttertiär - Verhandlungen der Geol Bundesanstalt, Wien, 1962/2, 363-377, Vienna 1962 STRADNER, H.: New contributions to Mesozoic stratigraphy by means of nannofossils - Proceedings of the Sixth World Petroleum Congress, Section 1, Paper (preprint), 167-184, 1963 STRADNER, H., ADAMIKER, D & MARESCH, O.: Electron Micro- scope Studies on Albian Calcareous Nannoplankton from the Delft and Leidschendam Deepwells, Holland - Verhandelingen der Koninklijke Nederlandse Akademie van Wetenschappen, Afd Natuurkunde, XXIV, 1-107, 1968 STRADNER, H & STEINMETZ, J.: Cretaceous calcareous nannofossils from the Angola Basin - Init Rep Deep Sea Drilling Project LXXV, Site 530, 565-649, 52 pis., 1984 TAYLOR, R J.: The distribution of calcareous nannofossils in the Speeton clay (Lower Cretaceous) of Yorkshire - Proceedings of the Yorkshire Geological Society, 42, 195-209, 1978a TAYLOR, R J.: The biostratigraphy of Lower Cretaceous calcareous nannoplankton from north-west Europe and North Africa - University of London unpublished thesis, 1-362, London 1978b TAYLOR, R J.: Lower Cretaceous (Ryanzanian to Albian) calcareous nannofossils In LORD, A R (Ed.): A stratigraphical Index of Calcareous Nannofossils - Brit Micropalaeontol Soc Ser., - , Chichester (Ellis Horwood Ltd.) 1982 TAYLOR, R J & HAMILTON, G B.: Preparation Techniques In LORD, A R (Ed.): A stratigraphical Index of Calcareous Nannofossils - Brit Micropalaeontol Soc Ser., 1 - , Chichester (Ellis Horwood Ltd.) 1982 THIERSTEIN, H R.: Tentative Lower Cretaceous Calcareous Nannoplankton Zonation - Eclogae Geologicae Helvetiae, 64, 459-488, 1971 THIERSTEIN, H R.: Lower Cretaceous Calcareous Nannoplankton Biostratigraphy - Abhandlungen der Geol Bundesanstalt Wien, 29, - , Vienna 1973 THIERSTEIN, H R.: Calcareous Nannoplankton - Leg 26, Deep Sea Drilling Project In DAVIES, T A., LUYENDYK, B P et al - Initial Reports of the Deep Sea Drilling Project, 26, XXVI, 619-667, Washington ( U S Govt Printing Office) 1974 THIERSTEIN, H R.: Mesozoic calcareous nannoplankton biostratigraphy of marine sediments - Marine Micropaleontology, 1, 325-362, 1976 THIERSTEIN, H R.: Late Cretaceous Nannoplankton and the change at the Cretaceous - Tertiary boundary S E P M Special Publication No 32, 355-394, 1981 VEKSHINA, V N.: Kokkolitoforidy Maastrikhtskikh otlozheniy Zapadno-Sibirskoy nizmennosti (Coccolithophoridae of the Maastrichtian deposits of the west Siberian Lowlands) - Tr Sibir Nauchno-lssled Inst Geologii, Geofizikii Mineral'nogo Syr'ya Trudy 2, - 7 , pis - , text-fig (in Russian) 1959 VERBEEK, J W.: Upper Cretaceous calcareous nannoplankton zonation in a composite section near El Kef, Tunisia I and II - Proceedings of the Koninklijke Nederlandse Akademie van Wetenschappen, B79, 129-148, 1976 VERBEEK, J W.: Calcareous nannoplankton biostratigraphy of Middle and Upper Cretaceous deposits in Tunisia, southern Spain and France - Utrecht Micropaleontological Bulletin, 16, 1-157, 1977 WIND, F H & WISE, S W.: Mesozoic and Cenozoic calcareous nannofossils recovered by D S D P Leg 36 drilling on the Falkland Plateau, Southwest Atlantic sector of the Southern Ocean - Initial Reports of the Deep Sea Drilling Project, XXXVI, 269-492, 1976 WORSLEY, T R.: Calcareous nannofossil zonation of Upper Jurassic and Lower Cretaceous sediments from the Western Atlantic - Proceedings of the II Planktonic Conference, Roma 1970, 2, 1301-1321, 1971 WOODLAND, A W (Ed.): Petroleum and the Continental Shelf of Northwest Europe, Vol 1, Geology - Applied Science Publications, 501 pp., London 1975 ZIEGLER, P A.: North-western Europe: tectonics and basin development - Geologie Mijnb 57, 589-626, 1978 175 ... V_-_ :_V_rV _v_r LV_-^ p7H BALDER FORMATION SELE FORMATION LISTA FORMATION 31 O a > o 30 MAUREEN FORMATION EKOFISK FORMATION o c LU U I 3< < 60.2 LIMESTONE: Hard t o Moderately hard, medium light... Fir« »oderately chalky texture, white, very pale orange, grading into fir« brittle, platy, light grey, pinkish grey, locally pyritic limestones S II LOWER 73 UPPER LOWER LltESTONE: Fir», moderately... use and relative importance of these subzones will be discussed in more detail under the relevant sections The reader is referred to the works of THIERSTEIN (1976), CRUX (1982), STRADNER & STEINMETZ